Medical imaging systems and associated devices and methods

ABSTRACT

Systems, methods, and devices for medical imaging are disclosed herein. In some embodiments, a method for imaging an anatomic region includes receiving, from a detector carried by an imaging arm of an x-ray imaging apparatus, a plurality of images of the anatomic region. The images can be obtained during manual rotation of the imaging arm. The imaging arm can be stabilized by a shim structure during the manual rotation. The method can also include receiving, from at least one sensor coupled to the imaging arm, pose data of the imaging arm during the manual rotation. The method can further include generating, based on the images and the pose data, a 3D representation of the anatomic region.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 18/175,275, filed Feb. 27, 2023, which is a continuation ofU.S. patent application Ser. No. 17/819,811, filed Aug. 15, 2022, nowU.S. Pat. No. 11,617,552, issued Apr. 4, 2023, which is a continuationof U.S. patent application Ser. No. 17/658,642, filed Apr. 8, 2022, nowU.S. Pat. No. 11,457,883, issued Oct. 4, 2022, which claims the benefitof priority to U.S. Provisional Application No. 63/172,886, filed Apr.9, 2021; U.S. Provisional Application No. 63/203,270, filed Jul. 15,2021; and U.S. Provisional Application No. 63/260,241, filed Aug. 13,2021; each of which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present technology relates generally to medical imaging, and inparticular, to systems for generating a three-dimensional (3D)representation of a patient's anatomy and associated methods anddevices.

BACKGROUND

3D anatomic models, such as computed tomography (CT) volumetricreconstructions, are frequently used in image-guided medical proceduresto allow the physician to visualize the patient anatomy in threedimensions and accurately position surgical tools at the appropriatelocations. However, 3D models generated from preprocedural image datamay not accurately reflect the actual anatomy at the time of theprocedure. Moreover, if the model is not correctly registered to theanatomy, it may be difficult or impossible for the physician to navigatethe tool to the right location, thus compromising the accuracy andefficacy of the procedure.

Cone-beam computed tomography (CBCT) has been used to generate highresolution, 3D volumetric reconstructions of a patient's anatomy forimage guidance during a medical procedure. However, many physicians donot have ready access to conventional CBCT imaging systems because thesesystems are extremely expensive and often reserved for use by specialtydepartments. While tomosynthesis (also known as limited-angletomography) has also been used for intraprocedural imaging, thistechnique is unable to produce 3D reconstructions with sufficiently highresolution for many procedures. Accordingly, improved medical imagingsystems and methods are needed.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present disclosure can be better understood withreference to the following drawings. The components in the drawings arenot necessarily to scale. Instead, emphasis is placed on clearlyillustrating the principles of the present disclosure.

FIGS. 1A-1E illustrate a system for imaging a patient in accordance withembodiments of the present technology.

FIGS. 2A and 2B illustrate examples of unwanted movements that may occurwith a manually-operated imaging apparatus.

FIGS. 3A and 3B illustrate a set of shim structures configured inaccordance with embodiments of the present technology.

FIGS. 3C and 3D illustrate shim structures having variable thicknessesin accordance with embodiments of the present technology.

FIGS. 4A and 4B illustrate a set of L-shaped shim structures configuredin accordance with embodiments of the present technology.

FIGS. 4C and 4D illustrate an adjustable L-shaped shim structureconfigured in accordance with embodiments of the present technology.

FIGS. 5A and 5B illustrate a set of U-shaped shim structures configuredin accordance with embodiments of the present technology.

FIGS. 5C and 5D illustrate an adjustable U-shaped shim structureconfigured in accordance with embodiments of the present technology.

FIGS. 6A and 6B illustrate another set of U-shaped shim structuresconfigured in accordance with embodiments of the present technology.

FIGS. 7A and 7B illustrate a shim structure with two arm regionsconfigured in accordance with embodiments of the present technology.

FIGS. 7C and 7D illustrate a shim structure with tapered arm regionsconfigured in accordance with embodiments of the present technology.

FIG. 7E illustrates a shim structure including a set of ridgesconfigured in accordance with embodiments of the present technology.

FIG. 7F illustrates a shim structure including a plurality ofprotrusions configured in accordance with embodiments of the presenttechnology.

FIG. 7G illustrates a shim structure including a plurality of square orrectangular notches configured in accordance with embodiments of thepresent technology.

FIG. 7H illustrates a shim structure including a plurality of triangularnotches configured in accordance with embodiments of the presenttechnology.

FIGS. 8A and 8B illustrate a set of shim structures with rollersconfigured in accordance with embodiments of the present technology.

FIGS. 9A-9F illustrate a shim structure with a mounting mechanismconfigured in accordance with embodiments of the present technology.

FIGS. 10A-10D illustrate another shim structure with a mountingmechanism configured in accordance with embodiments of the presenttechnology.

FIG. 11 is a graph illustrating motion of a motion sensor on a C-armdetector with and without shim stabilization.

FIG. 12 illustrates an example of unwanted movements that may occur witha manually-operated imaging apparatus.

FIGS. 13A and 13B illustrate a lever structure configured in accordancewith embodiments of the present technology.

FIG. 13C illustrates an adjustable lever structure configured inaccordance with embodiments of the present technology.

FIG. 13D illustrates another adjustable lever structure configured inaccordance with embodiments of the present technology.

FIGS. 14A and 14B illustrate a lever structure in accordance withembodiments of the present technology.

FIG. 14C illustrates another lever structure configured in accordancewith embodiments of the present technology.

FIGS. 14D and 14E illustrate an adjustable lever structure configured inaccordance with embodiments of the present technology.

FIG. 15 illustrates a motion sensor coupled to an imaging apparatus inaccordance with embodiments of the present technology.

FIG. 16 illustrates a motion sensor and a radiation sensor coupled to animaging apparatus in accordance with embodiments of the presenttechnology.

FIGS. 17A and 17B illustrate an attachment device configured inaccordance with embodiments of the present technology.

FIG. 17C illustrates the attachment device of FIGS. 17A and 17B coupledto an imaging apparatus, in accordance with embodiments of the presenttechnology.

FIG. 17D illustrates another attachment device configured in accordancewith embodiments of the present technology.

FIG. 17E illustrates another attachment device configured in accordancewith embodiments of the present technology.

FIGS. 18A and 18B illustrate a fiducial marker board for pose estimationin accordance with embodiments of the present technology.

FIG. 18C illustrates another fiducial marker board in accordance withembodiments of the present technology.

FIG. 18D illustrates yet another fiducial marker board in accordancewith embodiments of the present technology.

FIG. 18E illustrates another fiducial marker board in accordance withembodiments of the present technology.

FIGS. 18F and 18G illustrate a fiducial marker board and a phantom inaccordance with embodiments of the present technology.

FIG. 19 is a flow diagram illustrating a method for operating an imagingapparatus, in accordance with embodiments of the present technology.

FIG. 20 is a flow diagram illustrating a method for calibrating animaging apparatus, in accordance with embodiments of the presenttechnology.

FIGS. 21A-21D illustrate fiducial marker grids for distortion correctionin accordance with embodiments of the present technology.

FIG. 22A illustrates a fiducial marker phantom for geometric calibrationin accordance with embodiments of the present technology.

FIG. 22B illustrates another fiducial marker phantom configured inaccordance with embodiments of the present technology.

FIG. 22C illustrates an assembly that can form part of the fiducialmarker phantom of FIG. 22B, in accordance with embodiments of thepresent technology.

FIG. 22D illustrates another fiducial marker phantom configured inaccordance with embodiments of the present technology.

FIG. 23A is a flow diagram illustrating a method for imaging an anatomicregion, in accordance with embodiments of the present technology.

FIG. 23B is a flow diagram illustrating a method for generating a 3Dreconstruction, in accordance with embodiments of the presenttechnology.

FIG. 24 is a flow diagram illustrating a method of preparing an imagingapparatus for image acquisition, in accordance with embodiments of thepresent technology.

FIG. 25A is a flow diagram illustrating a method for calibration andimage acquisition using a fiducial marker board in accordance withembodiments of the present technology.

FIG. 25B is a flow diagram illustrating a method for operating animaging apparatus, in accordance with embodiments of the presenttechnology.

FIG. 26A is a CBCT image of a phantom generated by a manually-operatedimaging apparatus without calibration or shim stabilization.

FIG. 26B is a CBCT image of a phantom generated by a manually-operatedimaging apparatus with calibration and shim stabilization, in accordancewith embodiments of the present technology.

FIG. 27A is a CBCT image of a lung generated by a manually-operatedimaging apparatus without calibration or shim stabilization.

FIG. 27B is a CBCT image of a lung generated by a manually-operatedimaging apparatus with calibration and shim stabilization, in accordancewith embodiments of the present technology.

FIG. 27C is a CBCT image of a lung generated with a robotically-operatedCBCT imaging system.

DETAILED DESCRIPTION

The present technology generally relates to systems, methods, anddevices for medical imaging. For example, in some embodiments, thesystems and methods described herein use a mobile C-arm x-ray imagingapparatus (also referred to herein as a “mobile C-arm apparatus”) togenerate a 3D reconstruction of a patient's anatomy using CBCT imagingtechniques. Unlike conventional systems and devices that are specializedfor CBCT imaging, the mobile C-arm apparatus may lack a motor and/orother automated mechanisms for rotating the imaging arm that carries thex-ray source and detector. Instead, the imaging arm is manually rotatedthrough a series of different angles to obtain a sequence oftwo-dimensional (2D) projection images of the anatomy. In somesituations, the manual rotation may produce undesirable movements of theimaging arm (e.g., oscillations, vibrations, shifting, flexing) that caninterfere with the quality of the 3D reconstruction generated from the2D images. Additionally, the mobile C-arm apparatus may lack sensors forobtaining pose data of the imaging arm during image acquisition, whichmay be needed for an accurate 3D reconstruction.

Accordingly, in some embodiments, a method for imaging an anatomicregion includes receiving a plurality of 2D images of the anatomicregion from a detector carried by an imaging arm of an x-ray imagingapparatus (e.g., a mobile C-arm apparatus). The 2D images can beobtained during manual rotation of the imaging arm. The imaging arm canbe stabilized by a shim structure during the manual rotation to reduceor inhibit unwanted movements. The method can also include receivingsensor data indicative of a plurality of poses of the imaging arm duringthe manual rotation from at least one sensor coupled to the imaging arm(e.g., an inertial measurement unit (IMU)). The method can furtherinclude generating a 3D reconstruction of the anatomic region based onthe 2D images and the sensor data. The 3D reconstruction can bedisplayed to a physician or other operator to provide image-basedguidance during a medical procedure performed in the anatomic region(e.g., a biopsy or ablation procedure).

The embodiments described herein can provide many advantages overconventional imaging technologies. For example, the systems and methodsherein can use a manually-rotated mobile C-arm apparatus to generatehigh quality CBCT images of a patient's anatomy, rather than aspecialized CBCT imaging system. This approach can reduce costs andincrease the availability of CBCT imaging, thus allowing CBCT imagingtechniques to be used in many different types of medical procedures. Forexample, CBCT imaging can be used to generate intraprocedural 3D modelsof an anatomic region for guiding a physician in accurately positioninga tool at a target location in the anatomy, e.g., for biopsy, ablation,or other diagnostic or treatment procedures.

Embodiments of the present disclosure will be described more fullyhereinafter with reference to the accompanying drawings in which likenumerals represent like elements throughout the several figures, and inwhich example embodiments are shown. Embodiments of the claims may,however, be embodied in many different forms and should not be construedas limited to the embodiments set forth herein. The examples set forthherein are non-limiting examples and are merely examples among otherpossible examples.

As used herein, the terms “vertical,” “lateral,” “upper,” and “lower”can refer to relative directions or positions of features of theembodiments disclosed herein in view of the orientation shown in theFigures. For example, “upper” or “uppermost” can refer to a featurepositioned closer to the top of a page than another feature. Theseterms, however, should be construed broadly to include embodimentshaving other orientations, such as inverted or inclined orientationswhere top/bottom, over/under, above/below, up/down, and left/right canbe interchanged depending on the orientation.

Although certain embodiments of the present technology are described inthe context of medical procedures performed in the lungs, this is notintended to be limiting. Any of the embodiments disclosed herein can beused in other types of medical procedures, such as procedures performedon or in the musculoskeletal system, vasculature, abdominal cavity,gastrointestinal tract, genitourinary tract, brain, and so on.Additionally, any of the embodiments herein can be used for applicationssuch as surgical tool guidance, biopsy, ablation, chemotherapyadministration, surgery, or any other procedure for diagnosing ortreating a patient.

The headings provided herein are for convenience only and do notinterpret the scope or meaning of the claimed present technology.

I. Overview of Technology

Lung cancer kills more people each year than breast, prostate, and coloncancers combined. Most lung cancers are diagnosed at a late stage, whichcontributes to the high mortality rate. Earlier diagnosis of lung cancer(e.g., at stages 1-2) can greatly improve survival. The first step indiagnosing an early-stage lung cancer is to perform a lung biopsy on thesuspicious nodule or lesion. Bronchoscopic lung biopsy is theconventional biopsy route, but typically suffers from poor success rates(e.g., only 50% to 70% of nodules are correctly diagnosed), meaning thatthe cancer status of many patients remains uncertain even after thebiopsy procedure. One common reason for non-diagnostic biopsy is thatthe physician fails to place the biopsy needle into the correct locationin the nodule before collecting the biopsy sample. This situation canoccur due to shortcomings of conventional technologies for guiding thephysician in navigating the needle to the target nodule. For example,conventional technologies typically use a static chest CT scan of thepatient obtained before the biopsy procedure (e.g., days to weeksbeforehand) that is registered to the patient's anatomy during theprocedure (e.g., via electromagnetic (EM) navigation or shape sensingtechnologies). Registration errors can cause the physician to completelymiss the nodule during needle placement. These errors, also known asCT-to-body divergence, occur when the preprocedural scan data does notmatch the patient anatomy data obtained during the actual procedure.These differences can occur because the lungs are dynamic and oftenchange in volume from day-to-day and/or when patients are underanesthesia. Research has shown that the average error between thepreprocedural CT scan and the patient's anatomy during the procedure is1.8 cm, which is larger than many of the pulmonary nodules beingbiopsied.

CBCT is an imaging technique capable of producing high resolution 3Dvolumetric reconstructions of a patient's anatomy. For bronchoscopiclung biopsy, intraprocedural CBCT imaging can be used to confirm thatthe biopsy needle is positioned appropriately relative to the targetnodule and has been shown to increase diagnostic accuracy by almost 20%.A typical CBCT procedure involves scanning the patient's body with acone-shaped x-ray beam that is rotated over a wide, circular arc (e.g.,1800 to 360°) to obtain a sequence of 2D projection images. A 3Dvolumetric reconstruction of the anatomy can be generated from the 2Dimages using image reconstruction techniques such as filteredbackprojection or iterative reconstruction. Conventional CBCT imagingsystems include a motorized imaging arm for automated, highly-controlledrotation of the x-ray source and detector over a smooth, circular arcduring image acquisition. These systems are also capable of accuratelytracking the pose of the imaging arm across different rotation angles.However, CBCT imaging systems are typically large, extremely expensive,and may not be available to many physicians, such as pulmonologistsperforming lung biopsy procedures.

Manually-operated mobile C-arm apparatuses are less expensive and morereadily available than specialized CBCT imaging systems, but aregenerally unsuitable for CBCT imaging for some or all of the followingreasons. First, mobile C-arm apparatuses typically lack a motorizedimaging arm and thus must be manually rotated during imagingacquisition. However, with manual rotation, it is extremely difficult toproduce a smooth, isocentric, circular motion of the imaging arm oversufficiently large angles (e.g., greater than 90°) for CBCT imaging. Dueto mechanical instabilities present in many mobile C-arm apparatuses,the imaging arm may exhibit unwanted movements (e.g., oscillations,vibrations, shifts, flexing) during manual rotation, which may cause theimaging arm to move along a non-circular trajectory or otherwisedetrimentally affect the quality of the resulting 3D reconstruction.Second, mobile C-arm apparatuses generally lack the capability toaccurately determine the pose of the imaging arm as the imaging armrotates around the patient. In a typical CBCT imaging procedure,hundreds of images are acquired at a rate of 10-50 images per second,and the pose of the imaging arm needs to be determined for each image.Third, mobile C-arm apparatuses often use an image intensifier as thex-ray detector, which can create significant distortion artifacts thatprevent accurate image reconstruction. Image intensifiers are alsorelatively heavy (e.g., hundreds of pounds) and thus may furtherdestabilize the imaging arm during manual rotation.

Tomosynthesis is a technique that may be used to generateintraprocedural images of patient anatomy. However, becausetomosynthesis uses a much smaller rotation angle during imageacquisition (e.g., 15° to 70°), the resulting images are typically lowresolution, lack sufficient depth information, and/or may includesignificant distortion. Tomosynthesis is therefore typically notsuitable for applications requiring highly accurate 3D spatialinformation.

Accordingly, there is a need for imaging techniques that are capable ofproducing intraprocedural, high resolution 3D representations of apatient's anatomy using low-cost, accessible imaging systems such asmobile C-arm apparatuses. The present technology can address these andother challenges by providing systems, methods, and devices forperforming CBCT imaging using a manually-rotated imaging apparatus, alsoreferred to herein as “manually-rotated CBCT” or “mrCBCT.” For example,in some embodiments, the systems described herein mechanically stabilizethe imaging arm and/or other components of the mobile C-arm apparatususing one or more shim structures (e.g., wedges, blocks, dampers, etc.)that reduce or prevent unwanted movements during manual rotation. Thesystem can also include one or more lever structure (e.g., a detachableor permanently affixed handle) to assist the operator in rotating theimaging arm from locations that are less likely to produce unwantedmovements. The system can further include at least one sensor (e.g., amotion sensor such as an IMU) that automatically tracks the pose of theimaging arm during rotation. The sensor data can be temporallysynchronized to the obtained 2D projection images to accuratelydetermine the pose of the imaging arm for each image. In someembodiments, the system is calibrated before and/or during use tocorrect image distortion (e.g., from the image intensifier), determinecalibration parameters to compensate for mechanical differences betweenindividual mobile C-arm apparatuses, and/or adjust for variations in howthe operator manually rotates the imaging arm. The approaches describedherein can be used to adapt a manually-operated mobile C-arm apparatusfor CBCT imaging, thus allowing high quality CBCT reconstructions to beproduced using relatively inexpensive and accessible imaging equipment.

II. Medical Imaging Systems and Associated Devices and Methods

FIG. 1A is a partially schematic illustration of a system 100 forimaging a patient 102 in accordance with embodiments of the presenttechnology. The system 100 includes an imaging apparatus 104 operablycoupled to a console 106. The imaging apparatus 104 can be any suitabledevice configured to generate images of a target anatomic region of thepatient 102, such as an x-ray imaging apparatus. In the illustratedembodiment, for example, the imaging apparatus 104 is a mobile C-armapparatus configured for fluoroscopic imaging. A mobile C-arm apparatustypically includes a manually-movable imaging arm 108 configured as acurved, C-shaped gantry (also known as a “C-arm”). Examples of mobileC-arm apparatuses include, but are not limited to, the OEC 9900 Elite(GE Healthcare) and the BV Pulsera (Philips). In other embodiments,however, the techniques described herein can be adapted to other typesof imaging apparatuses 104 having a manually-movable imaging arm 108,such as a G-arm imaging apparatus.

The imaging arm 108 can carry a radiation source 110 (e.g., an x-raysource) and a detector 112 (e.g., an x-ray detector such as an imageintensifier or flat panel detector). The radiation source 110 can bemounted at a first end portion 114 of the imaging arm 108, and thedetector 112 can be mounted at a second end portion 116 of the imagingarm 108 opposite the first end portion 114. During a medical procedure,the imaging arm 108 can be positioned near the patient 102 such that thetarget anatomic region is located between the radiation source 110 andthe detector 112. The imaging arm 108 can be rotated to a desired pose(e.g., angle) relative to the target anatomic region. The radiationsource 110 can output radiation (e.g., x-rays) that travels through thepatient's body to the detector 112 to generate 2D images of the anatomicregion (also referred to herein as “projection images”). The image datacan be output as still or video images. In some embodiments, the imagingarm 108 is rotated through a sequence of different poses to obtain aplurality of 2D projection images. The images can be used to generate a3D representation of the anatomic region (also referred to herein as a“3D reconstruction,” “volumetric reconstruction,” “imagereconstruction,” or “CBCT reconstruction”). The 3D representation can bedisplayed as a 3D model or rendering, and/or as one or more 2D imageslices (also referred to herein as “CBCT images” or “reconstructedimages”).

In some embodiments, the imaging arm 108 is coupled to a base 118 by asupport arm 120. The base 118 can act as a counterbalance for theimaging arm 108, the radiation source 110, and the detector 112. Asshown in FIG. 1A, the base 118 can be a mobile structure includingwheels for positioning the imaging apparatus 104 at various locationsrelative to the patient 102. In other embodiments, however, the base 118can be a stationary structure. The base 118 can also carry variousfunctional components for receiving, storing, and/or processing theimage data from the detector 112, as discussed further below.

The support arm 120 (also referred to as an “attachment arm” or “pivotarm”) can connect the imaging arm 108 to the base 118. The support arm120 can be an elongate structure having a distal portion 122 coupled tothe imaging arm 108, and a proximal portion 124 coupled to the base 118.Although the support arm 120 is depicted in FIG. 1A as being an L-shapedstructure (“L-arm”) having a vertical section and a horizontal section,in other embodiments the support arm 120 can have a different shape(e.g., a curved shape).

The imaging arm 108 can be configured to rotate in multiple directionsrelative to the base 118. For example, FIG. 1B is a partially schematicillustration of the imaging apparatus 104 during an orbital rotation. Asshown in FIG. 1B, during an orbital rotation, the imaging arm 108rotates relative to the support arm 120 and base 118 along a lengthwisedirection as indicated by arrows 136. Thus, during an orbital rotation,the motion trajectory can be located primarily or entirely within theplane of the imaging arm 108. The imaging arm 108 can be slidablycoupled to the support arm 120 to allow for orbital rotation of theimaging arm 108. For example, the imaging arm 108 can be connected tothe support arm 120 via a first interface 126 that allows the imagingarm 108 to slide along the support arm 120.

FIG. 1C is a perspective view of the first interface 126, and FIG. 1D isa partially schematic cross-sectional view of the first interface 126along axis A-A in FIG. 1B. Referring to FIGS. 1C and 1D together, theimaging arm 108 can include a pair of rails 138 and a recessed track 140between the rails 138. The rails 138 can be located at opposite sides(e.g., a first side 142 and a second side 144) of the first interface126. The distal portion 122 of the support arm 120 can fit between therails 138 and at least partially into the track 140. The rails 138,track 140, and distal portion 122 can collectively form the firstinterface 126. As best seen in FIG. 1D, the distal portion 122 caninclude a pair of grooves or notches 146 that engage the rails 138 tosecure the distal portion 122 to the track 140. The distal portion 122can also include one or more wheels or rollers 148 that contact theinner surface of the track 140 so that the imaging arm 108 can slidesmoothly relative to the support arm 120 during orbital rotation.

FIG. 1E is a partially schematic illustration of the imaging apparatus104 during a propeller rotation (also known as “angular rotation” or“angulation”). As shown in FIG. 1E, during a propeller rotation, theimaging arm 108 and support arm 120 rotate relative to the base 118 in alateral direction as indicated by arrows 150. The support arm 120 can berotatably coupled to the base 118 via a second interface 128 (e.g., apivoting joint or other rotatable connection) that allows the imagingarm 108 and support arm 120 to turn relative to the base 118.Optionally, the imaging apparatus 104 can include a locking mechanism toprevent orbital rotation while the imaging arm 108 is performing apropeller rotation, and/or to prevent propeller rotation while theimaging arm 108 is performing an orbital rotation.

Referring again to FIG. 1A, the imaging apparatus 104 can optionally beconfigured to rotate in other directions, alternatively or in additionto orbital rotation and/or propeller rotation. For example, in someembodiments, the imaging arm 108 and the distal portion 122 of thesupport arm 120 are rotatable relative to the rest of the support arm120 and the base 118 (also known as “flip-flop” rotation). A flip-floprotation may be advantageous in some situations for reducinginterference with other components located near the operating table 152(e.g., a surgical robotic assembly).

The imaging apparatus 104 can be operably coupled to a console 106 forcontrolling the operation of the imaging apparatus 104. As shown in FIG.1A, the console 106 can be a mobile structure with wheels, thus allowingthe console 106 to be moved independently of the imaging apparatus 104.In other embodiments, however, the console 106 can be a stationarystructure. The console 106 can be attached to the imaging apparatus 104by wires, cables, etc., or can be a separate structure that communicateswith the imaging apparatus 104 via wireless communication techniques.The console 106 can include a computing device 130 (e.g., a workstation,personal computer, laptop computer, etc.) including one or moreprocessors and memory configured to perform various operations relatedto image acquisition and/or processing. For example, the computingdevice 130 can perform some or all of the following operations: receive,organize, store, and/or process data (e.g., image data, sensor data,calibration data) relevant to generating a 3D reconstruction; executeimage reconstruction algorithms; execute calibration algorithms; andpost-process, render, and/or display the 3D reconstruction. Additionalexamples of operations that may be performed by the computing device 130are described in greater detail elsewhere herein.

The computing device 130 can receive data from various components of thesystem 100. For example, the computing device 130 can be operablycoupled to the imaging apparatus 104 (e.g., to radiation source 110,detector 112, and/or base 118) via wires and/or wireless communicationmodalities (e.g., Bluetooth, WiFi) so that the computing device 130 cantransmit commands to the imaging apparatus 104 and/or receive data fromthe imaging apparatus 104. In some embodiments, the computing device 130transmits commands to the imaging apparatus 104 to cause the imagingapparatus 104 to start acquiring images, stop acquiring images, adjustthe image acquisition parameters, and so on. The imaging apparatus 104can transmit image data (e.g., the projection images acquired by thedetector 112) to the computing device 130. The imaging apparatus 104 canalso transmit status information to the computing device 130, such aswhether the components of the imaging apparatus 104 are functioningproperly, whether the imaging apparatus 104 is ready for imageacquisition, whether the imaging apparatus 104 is currently acquiringimages, etc.

Optionally, the computing device 130 can also receive other types ofdata from the imaging apparatus 104. In the embodiment of FIG. 1A, forexample, the imaging apparatus 104 includes at least one sensor 154configured to generate sensor data indicative of a pose of the imagingarm 108. The sensor data can be transmitted to the computing device 130via wired or wireless communication for use in the image processingtechniques described herein. Additional details of the configuration andoperation of the sensor 154 are provided below.

The console 106 can include various user interface components allowingan operator (e.g., a physician, nurse, technician, or other healthcareprofessional) to interact with the computing device 130. For example,the operator can input commands to the computing device 130 via asuitable input device (e.g., a keyboard, mouse, joystick, touchscreen,microphone). The console 106 can also include a display 132 (e.g., amonitor or touchscreen) for outputting image data, sensor data,reconstruction data, status information, control information, and/or anyother suitable information to the operator. Optionally, the base 118 canalso include a secondary display 134 for outputting information to theoperator.

Although FIG. 1A shows the console 106 as being separate from theimaging apparatus 104, in other embodiments the console 106 can bephysically connected to the imaging apparatus 104 (e.g., to the base118), such as by wires, cables, etc. Additionally, in other embodiments,the base 118 can include a respective computing device and/or inputdevice, such that the imaging apparatus 104 can also be controlled fromthe base 118. In such embodiments, the computing device located in thebase 118 can be configured to perform any of the image acquisitionand/or processing operations described herein. Optionally, the console106 can be integrated with the base 118 (e.g., the computing device 130is located in the base 118) or omitted altogether such that the imagingapparatus 104 is controlled entirely from the base 118. In someembodiments, the system 100 includes multiple consoles 106 (e.g., atleast two consoles 106), each with a respective computing device 130.Any of the processes described herein can be performed on a singleconsole 106 or across any suitable combination of multiple consoles 106.

A. Stabilization Devices and Methods

Referring again to FIG. 1A, the system 100 can be used to perform animaging procedure in which an operator manually rotates the imaging arm108 during imaging acquisition, such as an mrCBCT procedure. In suchembodiments, the imaging apparatus 104 can be a manually-operated devicethat lacks any motors or other actuators for automatically rotating theimaging arm 108. For example, one or both of the first interface 126 andsecond interface 128 can lack any automated mechanism for actuatingorbital rotation and propeller rotation of the imaging arm 108,respectively. Instead, the user manually applies the rotational force tothe imaging arm 108 and/or support arm 120 during the mrCBCT procedure.

In some embodiments, the imaging procedure involves performing apropeller rotation of the imaging arm 108. Propeller rotation may beadvantageous for mrCBCT or other imaging techniques that involverotating the imaging arm 108 over a relatively large rotation angle. Forexample, a mrCBCT or similar imaging procedure can involve rotating theimaging arm 108 over a range of at least 90°, 100°, 1100, 120°, 130°,140°, 150°, 160°, 170°, 180°, 190°, 200°, 210°, 220°, 230°, 240°, 250°,260°, 270°, 280°, 290°, 300°, 310°, 320°, 330°, 340°, 350°, or 360°. Thetotal rotation can be within a range from 900 to 360°, 900 to 270°, 900to 180°, 1200 to 360°, 1200 to 270°, 1200 to 180°, 1800 to 360°, or 1800to 270°. As previously discussed, the large rotation angle may berequired for capturing a sufficient number of images from differentangular or rotational positions to generate an accurate, high resolution3D reconstruction of the anatomy. In many situations, it is not possibleto achieve such large rotation angles using orbital rotation. Forexample, as shown in FIG. 1A, if the imaging apparatus 104 is positionedat one end of the patient's body (e.g., near the head and/or torso ofthe patient 102), the orbital rotation of the imaging arm 108 may beconstrained by the location of the patient 102 and/or the operatingtable 152 to a relatively limited rotation angle (e.g., less than 90°).

Larger rotation angles can be achieved with propeller rotation, even inthe configuration shown in FIG. 1A. However, propeller rotation can beless mechanically stable than orbital rotation, particularly when therotational force is applied manually. Accordingly, in the absence ofstabilization mechanisms (e.g., when shim structures 156 are omitted),the imaging arm 108 may exhibit unwanted movements during a manualpropeller rotation that can detrimentally affect the quality of theresulting CBCT reconstruction. Examples of unwanted movements that canoccur include, but are not limited to, oscillations, vibrations, suddenshifts, flexing, and/or other non-uniform motions that cause the imagingarm 108 to deviate from the desired trajectory (e.g., a smooth, singleplane, isocentric, and/or circular trajectory). Unwanted movements canoccur, for example, due to mechanical instability of the imagingapparatus 104 such as a weight imbalance between the radiation source110 and detector 112, as well as mechanical laxity in the firstinterface 126 and/or second interface 128. In some embodiments, thedetector 112 is much heavier than the radiation source 110 (e.g., animage intensifier can weigh hundreds of pounds). As a result, duringpropeller rotation, the imaging arm 108 can shift with respect to thesupport arm 120, and/or the support arm 120 can shift with respect tothe base 118. Such movements can cause the center of rotation of theimaging arm 108 to move during image acquisition, which can cause theprojection images obtained by the detector 112 to be misaligned. The 3Dreconstruction produced from such misaligned projection images mayinclude significant image artifacts and/or may lack sufficient spatialresolution for use in many medical procedures.

FIGS. 2A and 2B illustrate examples of unwanted movements that may occurat the first interface 126 during a manual propeller rotation of theimaging arm 108, in the absence of stabilization mechanisms. Referringto FIGS. 2A and 2B together, the first interface 126 can include spaces,gaps, etc., between the various components of the imaging arm 108 andsupport arm 120 (e.g., between the rails 138, track 140, distal portion122, grooves 146, and/or wheels 148). This mechanical laxity can allowthe imaging arm 108 and support arm 120 to shift relative to each other,even when the imaging arm 108 is locked to prevent orbital rotation. Forexample, the first and second sides 142, 144 of the first interface 126can each include a first gap 202, second gap 204, and/or third gap 206.The gaps 202-204 can be located between the rail 138 of the imaging arm108 and the groove 146 in the distal portion 122 of the support arm 120(in FIGS. 2A and 2B, the gaps 202-204 are labeled only on the secondside 144 merely for purposes of simplicity). In the illustratedembodiment, the first gap 202 is between a lower surface of the rail 138and an upper surface of the groove 146 and, the second gap 204 isbetween a lateral surface of the rail 138 and a lateral surface of thegroove 146, and the third gap 206 is between a lower surface of the rail138 and an upper surface of the groove 146. Due to the presence of thegaps 202-206, the imaging arm 108 can shift in a vertical direction 208(FIG. 2A) and/or a lateral direction 210 (FIG. 2B) relative to thesupport arm 120.

Referring again to FIG. 1A, in some embodiments, the system 100 includesfeatures for reducing or preventing unwanted movements that may occurduring a mrCBCT procedure. For example, the system 100 can include oneor more shim structures 156 for mechanically stabilizing certainportions of the imaging apparatus 104 (the shim structures 156 areomitted in FIGS. 1B-1E merely for purposes of simplicity). The shimstructures 156 can be removable or permanent components that are coupledto the imaging apparatus 104 at one or more locations to reduce orprevent unwanted movements during a manual rotation. In the illustratedembodiment, the system 100 includes two shim structures 156 positionedat opposite ends of the first interface 126 between the imaging arm 108and the support arm 120. Optionally, the system 100 can include fourshim structures 156, one at each end of the first interface 126 and onboth sides 142, 144 of the first interface 126. Alternatively or incombination, the system 100 can include one or more shim structures 156at other locations of the imaging apparatus 104 (e.g., at the secondinterface 128). Any suitable number of shim structures 156 can be used,such as one, two, three, four, five, six, seven, eight, nine, ten, 11,12, or more shim structures.

The shim structures 156 disclosed herein can make it easier for a userto produce a smooth, uniform movement of the imaging arm 108 over a widerotation angle without using motors or other automated actuationmechanisms. Accordingly, the projection images generated by the detector112 can exhibit significantly reduced misalignment compared toprojection images generated without the shim structures 156, thusimproving the accuracy and resolution of the resulting 3Dreconstruction. The shim structures 156 can also produce a moreconsistent rotation path of the imaging arm 108, which can significantlyimprove the accuracy of the calibration processes disclosed herein.Additional examples and features of shim structures 156 that can be usedwith the imaging apparatus 104 are described in greater detail below inconnection with FIGS. 3A-10D.

FIGS. 3A-10D illustrate representative examples of shim structures thatcan be used to stabilize an imaging apparatus, in accordance withembodiments of the present technology. Although the shim structures ofFIGS. 3A-10D are described and illustrated with reference to componentsof the imaging apparatus 104 of FIG. 1A, it will be appreciated that theshim structures can also be used with other imaging apparatuses andsystems. Additionally, any of the features of the shim structures ofFIGS. 3A-10D can be combined with each other.

FIG. 3A is a partially schematic cross-sectional view of the firstinterface 126 with a set of shim structures 302 a, 302 b configured inaccordance with embodiments of the present technology. Referring firstto FIG. 3A, the shim structures 302 a, 302 b can be used to stabilizethe first interface 126 between the imaging arm 108 and support arm 120of the imaging apparatus 104. In the illustrated embodiment, the shimstructures 302 a, 302 b are positioned at the first and second sides142, 144, respectively, of the first interface 126. The shim structures302 a, 302 b can fit within the first gaps 202 between the imaging arm108 and the support arm 120. The shim structures 302 a, 302 b canpartially or completely fill the first gaps 202, thus inhibiting orreducing unwanted movement of the imaging arm 108 relative to thesupport arm 120 when the imaging arm 108 is manually rotated. In someembodiments, the shim structures 302 a, 302 b are removable componentsthat are temporarily inserted into the first interface 126 to stabilizethe imaging arm 108 and support arm 120 during manual operation. Theshim structures 302 a, 302 b can be held in place by friction and/ormechanical interference, or by other mechanisms. In other embodiments,however, the shim structures 302 a, 302 b can be permanently affixedwithin the first interface 126.

FIG. 3B is a perspective view of an individual shim structure 302 a. Theshim structure 302 a can be an elongate member (e.g., a block, wedge,panel) configured to fill a space between the imaging arm 108 and thesupport arm 120. The shim structure 302 a can be made of any materialsuitable for dampening, obstructing, or otherwise preventing movement ofthe imaging arm 108 relative to the support arm 120, including rigid orcompliant materials. The geometry of the shim structure 302 a can alsobe varied as desired. In the illustrated embodiment, for example, theshim structure 302 a has a rectangular shape. In other embodiments, theshim structure 302 a can have any other suitable shape, such as square,trapezoidal, triangular, circular, oval, etc. The dimensions of the shimstructure 302 a can be configured to provide a desired fit between theimaging arm 108 and the support arm 120. For example, the shim structure302 a can have a length L₁ within a range from 1 cm to 20 cm, a width W₁within a range from 0.3 cm to 5 cm, and a thickness T₁ within a rangefrom 1 mm to 15 mm. The thickness T₁ can be equal or approximately equalto the height of the first gap 202 (FIG. 3A), and the length L₁ andwidth W₁ can be greater than or equal to the lateral dimensions of thefirst gap 202.

The shim structure 302 b can be identical or generally similar to theshim structure 302 a. For example, the shim structures 302 a, 302 b canboth have the same geometry (e.g., size, shape). In other embodiments,however, the shim structure 302 b can have a different geometry than theshim structure 302 a, e.g., the shim structure 302 b can be larger orsmaller than the shim structure 302 a, can have a different shape thanthe shim structure 302 a, etc. Optionally, either the shim structure 302a or shim structure 302 b can be omitted, such that only one of thesides of the first interface 126 includes a shim structure.

FIG. 3C is a side view of a shim structure 302 c having a variablethickness T₂, in accordance with embodiments of the present technology.The shim structure 302 c can be generally similar to the shim structure302 a and/or shim structure 302 b, except that the thickness T₂ of theshim structure 302 c decreases along the length L₂ of the shim structure302 c, such that the shim structure 302 c is thicker at a first endregion 304 and thinner at a second end region 306. In the illustratedembodiment, for example, the shim structure 302 c has a triangularcross-sectional shape, with the angle of the shim structure 302 c at thesecond end region 306 being less than or equal to 80°, 70°, 60°, 50°,45°, 40°, 35°, 30°, 25°, 20°, 15°, 10°, or 5°.

FIG. 3D is a partially schematic side view of a set of shim structures302 c, 302 c positioned at the first interface 126 in accordance withembodiments of the present technology. In the illustrated embodiment,the shim structure 302 d has tapered, wedge-like shape identical orsimilar to the shim structure 302 c. In other embodiments, however,either or both of the shim structures 302 c, 302 d can be replaced witha shim structure having a different shape, such as the rectangular shapeof the shim structure 302 a of FIG. 3B. As shown in FIG. 3D, the shimstructures 302 c, 302 d can be inserted into the spaces at the first andsecond ends 308, 310, respectively, of the first interface 126 betweenthe distal portion 122 of the support arm 120 and the imaging arm 108.Although FIG. 3D shows two shim structures 302 c, 302 d, in someembodiments, the first interface 126 can include a total of four shimstructures: two shim structures at both sides 142, 144 of the first end308, and two shim structures at both sides 142, 144 of the second end310.

FIG. 4A is a partially schematic cross-sectional view of the firstinterface 126 with a set of L-shaped shim structures 402 a, 402 b, andFIG. 4B is a perspective view of an individual shim structure 402 a, inaccordance with embodiments of the present technology. Referring toFIGS. 4A and 4B together, the shim structures 402 a, 402 b can beinserted between the imaging arm 108 and the support arm 120 at thefirst and second sides 142, 144 of the first interface 126,respectively. The shim structures 402 a, 402 b can each include a firstpanel 404 connected to a second panel 406 to form an L-shaped structure.The first panel 404 and second panel 406 can fit in the first gap 202and second gap 204, respectively, between the imaging arm 108 and thesupport arm 120. The first and second panels 404, 406 can be integrallyformed with each other as a single unitary component, or can be separatecomponents that are coupled to each other via adhesives, bonding,fasteners, etc. In the illustrated embodiment, the first and secondpanels 404, 406 are connected in a fixed geometry and are not movablerelative to each other. In other embodiments, however, the first andsecond panels 404, 406 can be movably coupled to each other, asdescribed further below.

The first and second panels 404, 406 can each be flattened, elongatemembers having a geometry (e.g., size, shape) selected to conform to theshape of the first and second gaps 202, 204. For example, the anglebetween the first and second panels 404, 406 can be greater than orequal to 10°, 20°, 30°, 40°, 45°, 50°, 60°, 70°, 80°, 90°, 100°, 110°,120°, 130°, 140°, 150°, 160°, or 170°. The first and second panels 404,406 can each have any suitable shape, such as rectangular, square, etc.The dimensions of the first and second panels 404, 406 can also bevaried as desired. In the illustrated embodiment, for example, the firstand second panels 404, 406 have the same length L₃ (e.g., within a rangefrom 1 cm to 20 cm) and thickness T₃ (e.g., within a range from 1 mm to15 mm), but have different widths W₃ and W₄, respectively. The width W₃of the first panel 404 can be greater than the width W₄ of the secondpanel 406. For example, the width W₃ can be within a range from 0.3 cmto 5 cm, and the width W₄ can be within a range from 0.1 cm to 3 cm. Inother embodiments, however, the width W₃ of the first panel 404 can beless than or equal to the width W₄ of the second panel 406. The firstand second panels 404, 406 can also have different lengths and/orthicknesses. Additionally, although the first and second panels 404, 406are both depicted as having a uniform thickness T₃, in otherembodiments, the first and/or second panels 404, 406 can instead have avariable thickness (e.g., a tapered thickness similar to the shimstructure 302 c of FIG. 3C).

FIGS. 4C and 4D are perspective views of an adjustable L-shaped shimstructure 402 c configured in accordance with embodiments of the presenttechnology. The shim structure 402 c includes a first panel 408 and asecond panel 410 connected to each other via an adjustable connection412. In the illustrated embodiment, the first and second panels 408, 410each have a rectangular or square flattened section 414 connected to atapered section 416. In other embodiments, the first and/or secondpanels 408, 410 can have a different shape, as discussed elsewhereherein. For example, the first panel 408 and second panel 410 can beidentical or similar to the first panel 404 and second panel 406 ofFIGS. 4A and 4B, respectively.

The adjustable connection 412 can be any attachment mechanism (e.g.,joint, hinge, pivot, etc.) that allows the first and second panels 408,410 to move (e.g., translate and/or rotate) independently relative toeach other. For example, as shown in FIGS. 4C and 4D, the adjustableconnection 412 can be a slidable connection that allows the first andsecond panels 408, 410 to slide relative to each other along alengthwise direction 418. In some embodiments, the adjustable connection412 is configured similarly to a sliding dovetail connection andincludes a rod or bolt on the edge of one panel (e.g., the first panel408) that slides within a receptacle or groove on the edge of the otherpanel (e.g., the second panel 410). The adjustable connection 412 canallow the first and second panels 408, 410 to slide relative to eachother for a predetermined distance (e.g., a distance within a range from3 cm to 5 cm). The adjustable connection 412 can include a hard stop toprevent the first and second panels 408, 410 from moving beyond thepredetermined distance and/or completely separating from each other.

During use, the adjustable connection 412 allows the first and secondpanels 408, 410 to be moved independently to provide an improved fitwith the first interface 126 (FIG. 4A). For example, the first andsecond panels 408, 410 can be sequentially inserted into the first gap202 and second gap 204, respectively, of the first interface 126. Insome embodiments, the shim structure 402 c is initially placed in apartially separated configuration as shown in FIG. 4C, with the secondpanel 410 displaced vertically relative to the first panel 408. Thefirst panel 408 can be inserted into the first gap 202 between theimaging arm 108 and the support arm 120. Next, the second panel 410 canbe moved downward and into alignment with the first panel 408 as shownin FIG. 4D, until the second panel 410 fits into the second gap 204between the imaging arm 108 and support arm 120. Alternatively, theorder can be reversed, with the second panel 410 being inserted beforethe first panel 408. The adjustable connection 412 can allow each panelto be advanced independently to the appropriate insertion depth forstabilization, which can be advantageous in situations where differentspaces within the first interface 126 have different dimensions.

FIG. 5A is a partially schematic cross-sectional view of the firstinterface 126 with a set of U-shaped shim structures 502 a, 502 bconfigured in accordance with embodiments of the present technology, andFIG. 5B is a perspective view of an individual shim structure 502 a.Referring to FIGS. 5A and 5B together, the shim structures 502 a, 502 bcan be inserted between the imaging arm 108 and the support arm 120 atthe first and second sides 142, 144 of the first interface 126,respectively. The shim structures 502 a, 502 b can each include a firstpanel 504, second panel 506, and third panel 508 that are connected toeach other to form a U-shaped structure. The shim structures 502 a, 502b can each be positioned so that the first panel 504 fills the first gap202, the second panel 506 fills the second gap 204, and the third panel508 fills the third gap 206. The first and third panels 504, 508 canengage the upper and lower surfaces of the rails 138 to secure the shimstructures 502 a, 502 b to the imaging arm 108. The panels 504-508 canbe integrally formed with each other as a single unitary component, orcan be separate components that are coupled to each other via adhesives,bonding, fasteners, etc. In the illustrated embodiment, the panels504-508 are connected in a fixed geometry and are not movable relativeto each other. In other embodiments, however, some or all of the panels504-508 can be movably coupled to each other, as described furtherbelow.

The panels 504-508 can each be flattened, elongate members having ageometry (e.g., size, shape) selected to conform to the shape of thegaps 202-206, respectively. For example, the angle between a pair ofconnected panels (e.g., the first and second panels 504, 506; the secondand third panels 506, 508) can each independently be greater than orequal to 10°, 20°, 30°, 40°, 45°, 50°, 60°, 70°, 80°, 90°, 100°, 110°,120°, 130°, 140°, 150°, 160°, or 170°. The panels 504-508 can each haveany suitable shape, such as rectangular, square, etc. The dimensions ofthe panels 504-508 can also be varied as desired. In the illustratedembodiment, for example, the panels 504-508 have the same lengthL_(s)(e.g., within a range from 1 cm to 20 cm) and thickness T₅ (e.g.,within a range from 1 mm to 15 mm), but different widths W₅, W₆, and W₇,respectively. For example, the width W₅ of the first panel 504 can begreater than or equal to the width W₇ of the third panel 508, which canbe greater than the width W₆ of the second panel 506. For example, thewidth W₅ can be within a range from 0.3 cm to 5 cm, the width W₆ can bewithin a range from 0.1 cm to 3 cm, and the width W₇ can be within arange from 0.3 cm to 5 cm. In other embodiments, however, the panels504-508 can have different dimensions, e.g., the width W₆ can be greaterthan or equal to the width W_(s) and/or the width W₇, some or all of thepanels 504-508 can have different lengths, etc. Additionally, althoughthe panels 504-508 are each depicted as having a uniform thickness T₅,in other embodiments, some or all of the panels 504-508 can instead havea variable thickness (e.g., a tapered thickness similar to the shimstructure 302 c of FIG. 3C).

FIGS. 5C and 5D are perspective views of a U-shaped shim structure 502 cwith slidable connections configured in accordance with embodiments ofthe present technology. The shim structure 502 c includes a first panel510, second panel 512, and third panel 514 connected to each other via afirst adjustable connection 516 and a second adjustable connection 518.The first and second panels 510, 512 can be coupled along their lateraledges by the first adjustable connection 516, and the second and thirdpanels 512, 514 can be coupled their lateral edges by the secondadjustable connection 518. In the illustrated embodiment, the panels510-514 each have a rectangular or square flattened section connected toa tapered section. In other embodiments, some or all of the panels510-514 can have a different shape, as discussed elsewhere herein.Optionally, the panels 510-514 can be identical or similar to the panels504-508 of FIGS. 5A and 5B, respectively.

The first and second adjustable connections 516, 518 can each includeany suitable attachment mechanism (e.g., joint, hinge, pivot, etc.) thatallows the corresponding panels to move (e.g., translate and/or rotate)independently relative to each other. For example, as shown in FIGS. 5Cand 5D, the first and second adjustable connections 516, 518 can both beslidable connections (e.g., slidable dovetail connections) that allowthe panels 510-514 to translate relative to each other, e.g., along alengthwise direction 520. The first and second adjustable connections516, 518 can include any of the features described above with respect tothe adjustable connection 412 of FIGS. 4C and 4D.

The first and second adjustable connections 516, 518 can allow thepanels 510-512 to be moved independently to provide an improved fit withthe first interface 126. For example, the panels 510-514 can besequentially inserted into the gaps 202-206, respectively, of the firstinterface 126 (FIG. 5A). In some embodiments, the shim structure 502 cis initially placed in a partially separated configuration, such as theconfiguration shown in FIG. 5C with the first panel 510 and third panel514 displaced vertically relative to the second panel 512. The panels510-514 can then be sequentially inserted into the corresponding gaps202-206 in any suitable order. For example, the second panel 512 can beinserted before the first and third panels 510, 514; and then the firstpanel 510 can be inserted before the third panel 514, or vice-versa. Asanother example, the first panel 510 can be inserted first, followed bythe second panel 512, and then the third panel 514. When the shimstructure 502 c is fully inserted, the panels 510-514 can be generallyaligned with each other, e.g., as shown in the configuration of FIG. 5D.

FIG. 6A is a partially schematic cross-sectional view of the firstinterface 126 with a set of U-shaped shim structures 602 a, 602 bconfigured in accordance with embodiments of the present technology, andFIG. 6B is a perspective view of an individual shim structure 602 a.Referring to FIGS. 6A and 6B together, the shim structures 602 a, 602 bcan be inserted between the imaging arm 108 and the support arm 120 atthe first and second sides 142, 144 of the first interface 126,respectively. The shim structures 602 a, 602 b can each include a firstpanel 604, second panel 606, and third panel 608 that are connected toeach other to form a U-shaped structure. The shim structures 602 a, 602b can each be positioned so that the first panel 604 fills the first gap202, the second panel 606 fills the second gap 204, and the third panel608 extends along an outer surface of the imaging arm 108 near the rail138. In some embodiments, the first and second panels 604, 606 caninhibit movement of the imaging arm 108 relative to the support arm 120,while the third panel 608 can engage the outer surface of the rail 138to secure the shim structures 602 a, 602 b in place.

The panels 604-608 can be integrally formed with each other as a singleunitary component, or can be separate components that are coupled toeach other via adhesives, bonding, fasteners, etc. In some embodiments,the panels 604-608 are connected in a fixed geometry and are not movablerelative to each other. In other embodiments, some or all of the panels604-608 can be movably coupled to each other via adjustable connections,as previously described with reference to FIGS. 5C and 5D.

The panels 604-608 can each be flattened, elongate members having ageometry (e.g., size, shape) selected to conform to the shape of thegaps 202, 204 and the outer surface of the imaging arm 108. For example,the angle between any pair of connected panels (e.g., the first andsecond panels 604, 606; the first and third panels 604, 608) can eachindependently be greater than or equal to 10°, 20°, 30°, 40°, 45°, 50°,60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, or 170°.The panels 604-608 can each have any suitable shape, such asrectangular, square, etc. The dimensions of the panels 604-608 can alsobe varied as desired. In the illustrated embodiment, for example, thepanels 604-608 have the same length L₈ (e.g., within a range from 1 cmto 20 cm) and thickness T₈ (e.g., within a range from 1 mm to 15 mm),but different widths W₈, W₉, and W₁₀, respectively. The width W₈ of thefirst panel 604 can be greater than the width W₉ of the second panel 606and/or the width W₁₀ of the third panel 608. The width W₉ of the secondpanel 606 can be equal to or greater than the width W₁₀ of the thirdpanel 608. In some embodiments, the width W₈ is within a range from 0.3cm to 5 cm, the width W₉ is within a range from 0.1 cm to 3 cm, and thewidth W₁₀ is within a range from 0.1 cm to 3 cm. In other embodiments,however the panels 604-608 can have different dimensions, e.g., thewidth W₈ can be less than or equal to the width W₉ and/or the width W₁₀,some or all of the panels 604-608 can have different lengths, etc.Additionally, although the panels 604-608 are each depicted as having auniform thickness T₈, in other embodiments, some or all of the panels604-608 can instead have a variable thickness (e.g., a tapered thicknesssimilar to the shim structure 302 c of FIG. 3C).

FIG. 7A is a partially schematic cross-sectional view of the firstinterface 126 with a shim structure 702 a and FIG. 7B is a perspectiveview of the shim structure 702 a, in accordance with embodiments of thepresent technology. Referring to FIGS. 7A and 7B together, the shimstructure 702 a includes a first arm region 704 and a second arm region706 connected to each other by a bridge region 708 to form a flattened,horseshoe-shape or U-shaped structure. The first arm region 704 can be aflattened, elongate member (e.g., a panel, block, wedge) including afirst end portion 712 coupled to one side of the bridge region 708, anda second end portion 714 spaced apart from the bridge region 708.Similarly, the second arm region 706 can be a flattened, elongate member(e.g., a panel, block, wedge) including a first end portion 716 coupledto the other side of the bridge region 708, and a second end portion 718spaced apart from the bridge region 708. As best seen in FIG. 7A, thefirst and second arm regions 704, 706 can fit into the first gaps 202 atthe first and second sides 142, 144 of the first interface 126,respectively to stabilize the imaging arm 108 and support arm 120. Thefirst and second arm regions 704, 706 can be generally similar to theshim structures 302 a, 302 b of FIG. 3A, except that the first andsecond arm regions 704, 706 are connected to each other by the bridgeregion 708, rather than being separate, discrete structures.

The bridge region 708 can be a flattened, elongate member (e.g., panel,block, strip, connector, etc.) that extends laterally from the firstside 142 of the first interface 126 to the second side 144 of the firstinterface 126 to join the first and second arm regions 704, 706 to eachother. The regions 704-708 can be integrally formed with each other as asingle unitary component, or can be separate components that are coupledto each other via adhesives, bonding, fasteners, etc. The regions704-708 can be connected to each other in a fixed geometry, or can bemovably coupled to each other via adjustable (e.g., slidable)connections as discussed elsewhere herein.

In some embodiments, the first and second arm regions 704, 706 inhibitmovement of the imaging arm 108 relative to the support arm 120, whilethe bridge region 708 secures the first and second arm regions 704, 706in place, e.g., by applying an inward force on the first and second armregions 704, 706 during rotation of the imaging arm 108. The bridgeregion 708 can also be beneficial for ensuring that the first and secondarm regions 704, 706 are positioned at substantially the same insertiondepth into the first gaps 202 at both sides 142, 144 of the firstinterface 126. Optionally, the shim structure 702 a can also include ahandle connected to the bridge region 708 (not shown) to facilitateinsertion and/or removal of the shim structure 702 a from the firstinterface 126.

The geometry (e.g., size, shape) of the first and second arm regions704, 706 can be selected to conform to the shape of the first gaps 202.Additionally, the geometry and configuration of the regions 704-708 candefine a recess or cavity 710 in the shim structure 702 a thataccommodates the outer surface of the distal portion 122 of the supportarm 120 and/or the imaging arm 108. In the illustrated embodiment, thefirst and second arm regions 704, 706 and the bridge region 708 eachhave a rectangular shape. In other embodiments, however, any of theregions 704-708 can have a different shape (e.g., square, triangular,etc.). The dimensions of the regions 704-708 can also be varied asdesired. In the illustrated embodiment, for example, the first andsecond arm regions 704, 706 have the same length L₁₁ (e.g., within arange from 1 cm to 20 cm), width W₁₁ (e.g., within a range from 0.3 cmto 5 cm), and thickness T₁₁ (e.g., within a range from 1 mm to 15 mm).Alternatively, the first and second arm regions 704, 706 can havedifferent lengths, widths, and/or thicknesses.

The bridge region 708 can have a length L₁₂ that is less than the lengthL₁₁ of the first and second arm regions 704, 706. For example, thelength L₁₂ can be less than or equal to 10 cm, or within a range from 5cm to 0.3 cm. The bridge region 708 can have a width W₁₂ that is greaterthan or equal to the width W₁₁ of the first and second arm regions 704,706. For example, the width W₁₂ can be within a range from 5 cm to 10cm, or from 3 cm to 10 cm. In other embodiments, however, the width W₁₂can be less than the width W₁₁ of the first and second arm regions 704,706. The bridge region 708 can have the same thickness T₁₁ as the firstand second arm regions 704, 706 or can have a different (e.g., larger orsmaller) thickness.

FIG. 7C is a perspective view of a shim structure 702 b configured inaccordance with embodiments of the present technology. The shimstructure 702 b can be identical or generally similar to the shimstructure 702 a of FIGS. 7A and 7B, except that the first arm region 704and second arm region 706 each have a tapered and/or wedge-like shape.As shown in FIG. 7C, the first and second arm regions 704, 706 each havea first thickness T₁₃ at their first end portions 712, 716, and a secondthickness T₁₄ at their second end portions 714, 718. The first thicknessT₁₃ can be greater than the second thickness T₁₄. For example, the firstthickness T₁₃ can be at least 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm,10 mm, or 15 mm, or within a range from 4 mm to 8 mm. The secondthickness T₁₄ can be less than 5 mm, 4 mm, 3 mm, 2 mm, 1 mm, 0.5 mm, or0.1 mm, or within a range from 4 mm to 0.1 mm. Optionally, the first andsecond arm regions 704, 706 can each be tapered to have a triangularcross-sectional shape (e.g., similar to the shim structure 302 c of FIG.3C), with the angle at the respective second end portion 714, 718 beingless than or equal to 80°, 70°, 60°, 50°, 45°, 40°, 35°, 30°, 25°, 20°,15°, 10°, or 5°.

FIG. 7D is a perspective view of the shim structure 702 b positioned atthe first interface 126 in accordance with embodiments of the presenttechnology. As shown in FIG. 7D, the shim structure 702 b is positionedat one end of the first interface 126, with the first and second armregions 704, 706 inserted into the spaces between the imaging arm 108and the distal portion 122 of the support arm 120, and the bridge region708 extending laterally across the imaging arm 108. The presence of thebridge region 708 can help the user visually confirm whether the firstand second arm regions 704, 706 are positioned at the substantially thesame insertion depth within the first interface 126, which can bebeneficial for improving mechanical stability during manual rotation.Optionally, another shim structure identical or similar to the shimstructure 702 b can be positioned at the other end of the firstinterface 126 (not shown in FIG. 7D).

FIGS. 7E-7H illustrate additional shim structures 702 c-702 f configuredin accordance with embodiments of the present technology. The shimstructures 702 c-702 f can be generally similar to the shim structures702 a, 702 b of FIGS. 7A-7D. Accordingly, the discussion of the shimstructures 702 c-702 f will be limited to those features that differfrom the embodiments of FIGS. 7A-7D. Additionally, any of the featuresof the shim structures 702 c-702 f can be combined with the embodimentof FIGS. 7A-7D and/or with each other.

FIG. 7E is a perspective view of a shim structure 702 c including a setof ridges 720 configured in accordance with embodiments of the presenttechnology. The ridges 720 can be elongated, raised structures locatedat or near the inner edges of the first and second arm regions 704, 706.In the illustrated embodiment, each ridge 720 extends only partiallyalong the length of the respective first or second arm region 704, 706,and terminates before the location where the arm region connects to thebridge region 708. In other embodiments, however, each ridge 720 canextend along the entire length of the respective first or second armregion 704, 706. When the shim structure 702 c is inserted into thefirst interface 126, the ridges 720 can extend above the surfaces of thefirst and second arm regions 704, 706 to further secure the shimstructure 702 c in place.

FIG. 7F is a perspective view of a shim structure 702 d including aplurality of protrusions 722 configured in accordance with embodimentsof the present technology. As shown in FIG. 7F, the protrusions 722 arelocated along the inner surfaces of the first and second arm regions704, 706 and extend inward into the recess 710. When the shim structure702 d is positioned at the first interface 126, the protrusions 722 canengage the distal portion 122 of the support arm 120 to secure the shimstructure 702 d in place. The shim structure 702 d can include anysuitable number of protrusions 722, such as one, two, three, four, five,ten, fifteen, twenty, or more protrusions 722. Although the protrusions722 are depicted as being rounded, semi-circular bumps, in otherembodiments the protrusions 722 can have a different shape, such assquare, rectangular, triangular, etc. Optionally, the protrusions 722can be angled toward the bridge region 708 to further lock the shimstructure 702 d into place. The dimensions and spacing of theprotrusions 722 can also be varied as desired. For example, theprotrusions 722 can each have a width and/or height within a range from1 mm to 10 mm, and can be spaced apart from each other by a distancewithin a range from 1 mm to 10 mm.

FIG. 7G is a perspective view of a shim structure 702 e including aplurality of square or rectangular notches 724. As shown in FIG. 7G, thenotches 724 are located along the inner surfaces of the first and secondarm regions 704, 706. The notches 724 can create a tooth-like texturealong the inner surfaces of the first and second arm regions 704, 706 toimprove engagement between the shim structure 702 e and the support arm120. The shim structure 702 e can include any suitable number of notches724, such as one, two, three, four, five, ten, fifteen, twenty, or morenotches 724. The dimensions and spacing of the notches 724 can be variedas desired, e.g., the notches 724 can each have a width and/or depthwithin a range from 1 mm to 10 mm, and can be spaced from each other bya distance within a range from 1 mm to 10 mm.

FIG. 7H is a perspective view of a shim structure 702 f including aplurality of triangular notches 726. The notches 726 can be oriented sothat the base of each triangular notch 726 is connected to the recess710 and the apex of each triangular notch 726 points away from therecess 710. The spacing, size, and function of the notches 726 canotherwise be generally similar to the square or rectangular notches 724of FIG. 7G.

In some embodiments, when the shim structures described herein areplaced in the first interface 126 between the imaging arm 108 andsupport arm 120, the shim structure can reduce or prevent the imagingarm 108 from sliding relative to the support arm 120, thus inhibitingorbital rotation of the imaging arm 108. Alternatively, the shimstructures described herein can be configured to permit orbital rotationof the imaging arm 108, which may improve convenience and ease of use.

FIG. 8A is a partially schematic cross-sectional view of the firstinterface with a set of shim structures 802 a, 802 b with rollers 804,and FIG. 8B is a perspective view of an individual shim structure 802 a,in accordance with embodiments of the present technology. The shimstructures 802 a, 802 b can each include a panel 806, e.g., similar tothe shim structures 302 a, 302 b of FIGS. 3A and 3B. One or more rollers804 (e.g., wheels, ball bearings, etc.) can be embedded in or otherwisecoupled to the panel 806. The rollers 804 can protrude out of the upperand/or lower surfaces of the panel 806. Accordingly, when the shimstructure 802 a, 802 b are inserted in the first interface 126, therollers 804 can contact the surfaces of the imaging arm 108 and/orsupport arm 120 to allow these components to slide relative to eachother. In the illustrated embodiment, for example, the rollers 804contact the lower surfaces of the rails 138 of the imaging arm 108 andthe upper surfaces of the grooves 146 formed in the distal portion 122of the support arm 120. Thus, the imaging arm 108 can still be rotatedin an orbital rotation direction while being stabilized by the shimstructures 802 a, 802 b for propeller rotation.

In some embodiments, the shim structures described herein are configuredto be permanently or temporarily attached to the imaging apparatus 104,even when not in use. For example, the shim structure can be coupled toa portion of the imaging apparatus 104 (e.g., to the imaging arm 108)via a mounting mechanism. The mounting mechanism can allow the shimstructure to be moved between an engaged configuration, in which theshim structure is stabilizing the imaging apparatus 104 for manualrotation as described elsewhere herein, and a disengaged configuration,in which the shim structure remains attached to the imaging apparatus104 by the mounting mechanism but is not stabilizing the imagingapparatus 104. In the disengaged configuration, the components of theimaging apparatus 104 (e.g., the imaging arm 108 and support arm 120)can move freely relative to each other without being obstructed by theshim structure. This approach allows the operator to quickly and easilyswitch between stabilized and non-stabilized operation of the imagingapparatus 104, while reducing the likelihood of the shim structure beinglost when not in use.

FIGS. 9A-9F illustrate a shim structure 902 with a mounting mechanism904 configured in accordance with embodiments of the present technology.Referring first to FIG. 9A, which is a partially schematic top view ofthe shim structure 902, the shim structure 902 is a flattened, U-shapedstructure that is generally similar to the shim structures 702 a and 702b of FIGS. 7A-7D. For example, the shim structure 902 can include afirst arm region 906, a second arm region 908, and a bridge region 910connecting the first and second arm regions 906, 908. The shim structure902 can optionally include a handle 912 coupled to the bridge region 910to allow an operator to engage and disengage the shim structure 902 fromthe first interface 126 of the imaging apparatus 104, as describedfurther below.

In some embodiments, the mounting mechanism 904 is also a flattened,U-shaped structure including a respective first arm region 914, secondarm region 916, and bridge region 918. The first arm region 914 of themounting mechanism 904 can be coupled to the first arm region 906 of theshim structure 902 via a first hinge 920, and the second arm region 916of the mounting mechanism 904 can be coupled to the second arm region908 of the shim structure 902 via a second hinge 922. The bridge region918 can be a bar or similar structure that engages a portion of theimaging apparatus 104 to prevent the shim structure 902 from beingremoved from the imaging arm 108.

FIGS. 9B and 9C are partially schematic side views of the shim structure902 and mounting mechanism 904 in a straightened state (FIG. 9B) and abent state (FIG. 9C). As shown in FIG. 9B, in the straightened state,the longitudinal axis of the shim structure 902 can be generally alignedwith (e.g., parallel to) the longitudinal axis of the mounting mechanism904. As shown in FIG. 9C, in the bent state, the shim structure 902 canpivot relative to the mounting mechanism 904 around the first and secondhinges 920, 922, such that the longitudinal axis of the shim structure902 is offset from (e.g., perpendicular to) the longitudinal axis of themounting mechanism 904.

FIGS. 9D-9F are partially schematic side views of the shim structure 902and mounting mechanism 904 during use, in accordance with embodiments ofthe present technology. Referring first to FIG. 9D, the mountingmechanism 904 can be positioned at the first interface 126 between theimaging arm 108 and the distal portion 122 of the support arm 120. Insome embodiments, the bridge region 918 of the mounting mechanism 904 isinserted into the grooves 146 (FIG. 1C) between the distal portion 122of the support arm 120 and the rails 138 (FIG. 1C) of the imaging arm108, in an orientation extending laterally across the track 140 (FIG.1C) of the imaging arm 108. Accordingly, the distal portion 122 of thesupport arm 120 located within the track 140 can obstruct the mountingmechanism 904, and thus, the shim structure 902, from being removed fromthe first interface 126. In such embodiments, the shim structure 902 canbe coupled to the mounting mechanism 904 after the mounting mechanism904 has been inserted into the first interface 126.

When stabilization is not needed, the shim structure 902 can be placedin a disengaged configuration as shown in FIG. 9D. In the disengagedconfiguration, the shim structure 902 is positioned out of and away fromthe first interface 126. To prevent the shim structure 902 frominadvertently sliding into the first interface 126 (e.g., due to gravityor if bumped by an operator), the shim structure 902 can be rotated intothe bent state. In some embodiments, the bridge region 918 of themounting mechanism 904 is sufficiently low-profile such that the imagingarm 108 can move relative to the support arm 120 (e.g., along an orbitalrotation direction) when the shim structure 902 is in the disengagedconfiguration.

Referring next to FIG. 9E, when stabilization is desired, the operatorcan rotate the shim structure 902 into the straightened state using thehandle 912. Subsequently, the operator can place the shim structure 902into an engaged configuration as shown in FIG. 9F by advancing the shimstructure 902 into the first interface 126 using the handle 912. In theengaged configuration, the first and second arm regions 906, 908 of theshim structure 902 can be positioned in the gaps between the support arm120 and imaging arm 108 to inhibit unwanted movements, as describedelsewhere herein. Once the imaging procedure is complete, the shimstructure 902 can be retracted out of the first interface 126 and foldedback into the disengaged configuration of FIG. 9D.

FIG. 10A is a partially schematic cross-sectional view of the firstinterface 126 of imaging apparatus 104 with a shim structure 1002 andmounting mechanism 1004, and FIG. 10B is a front view of the shimstructure 1002 and mounting mechanism 1004, in accordance withembodiments of the present technology. As best seen in FIG. 10B, theshim structure 1002 is a flattened, U-shaped structure that is generallysimilar to the shim structures 702 a and 702 b of FIGS. 7A-7D. Forexample, the shim structure 1002 can include a first arm region 1006, asecond arm region 1008, and a bridge region 1010 connecting the firstand second arm regions 1006, 1008.

Referring to FIGS. 10A and 10B together, the mounting mechanism 1004includes a first knob 1012 attached to a first gear 1014 that is coupledto the first arm region 1006 of the shim structure 1002, and a secondknob 1016 attached to a second gear 1018 that is coupled to the secondarm region 1008 of the shim structure 1002. The first and second knobs1012, 1016 can each be rotated by an operator to turn the first andsecond gears 1014, 1018, which in turn translate the shim structure 1002between a disengaged configuration and an engaged configuration, asdescribed further below. Optionally, the first and second gears 1014,1018 can be coupled to each other via a connector 1020 (e.g., acrossbar), such that the first and second arm regions 1006, 1008 areconcurrently translated even when only one of the knobs 1012, 1016 isrotated. This configuration can be advantageous for ensuring that thefirst and second arm regions 1006, 1008 are advanced into the gaps atthe first and second sides 142, 144, respectively, of the firstinterface 126 (FIG. 10A) by the same or similar distances.

FIGS. 10C and 10D are partially schematic side views of the shimstructure 1002 and mounting mechanism 1004 during use, in accordancewith embodiments of the present technology. Referring first to FIG. 10C,the mounting mechanism 904 can be positioned at the first interface 126between the imaging arm 108 and the distal portion 122 of the supportarm 120. In some embodiments, the connector 1020 of the mountingmechanism 1004 is inserted into the grooves 146 (FIG. 1C) between thedistal portion 122 of the support arm 120 and the rails 138 (FIG. 1C) ofthe imaging arm 108, in an orientation extending laterally across thetrack 140 (FIG. 1C) of the imaging arm 108. Alternatively, the connector1020 can be positioned outside and laterally across the distal portion122 of the support arm 120.

When stabilization is not needed, the shim structure 1002 can be placedin a disengaged configuration as shown in FIG. 10C. In the disengagedconfiguration, the shim structure 1002 is positioned out of and awayfrom the first interface 126. When stabilization is desired, theoperator can rotate the first and/or second knobs 1012, 1016 of themounting mechanism 1004 to place the shim structure 1002 into an engagedconfiguration as shown in FIG. 10D. The rotation of the first and/orsecond knobs 1012, 1016 can turn the first and/or second gears 1014,1018 to advance the shim structure 1002 forward relative to the mountingmechanism 1004 and into the first interface 126. In the engagedconfiguration, the first and second arm regions 1006, 1008 of the shimstructure 1002 can be positioned in the gaps between the support arm 120and imaging arm 108 to inhibit unwanted movements, as describedelsewhere herein. Once the imaging procedure is complete, the firstand/or second knobs 1012, 1016 can be rotated in the reverse directionto turn the first and/or second gears 1014, 1018 backward to retract theshim structure 1002 relative to the mounting mechanism 1004 and out ofthe first interface 126.

FIG. 11 is a graph illustrating motion of an IMU on a C-arm detectorwith and without shim stabilization. The motion data was generated by anIMU with an accelerometer while the C-arm was manually rotated through acontinuous 1800 propeller rotation. The x-axis represents the rotationalposition of the C-arm as measured by the IMU. The y-axis represents thedegree of off-plane motion of the IMU during the rotation (e.g.,unwanted motion). In the illustrated embodiment, there is ideally littleor no off-plane motion (e.g., line 1102), indicating that the detectoris moving within a single rotational plane. In the absence of shimstructures (line 1104), the IMU motion data includes significantoscillations and sharp changes in slope, corresponding to sudden weightshifts and reverberations that occur due to mechanical laxity and weightimbalances between the C-arm detector and source. These movements can bevariable and inconsistent between rotations, which can make it difficultor impossible to compensate for such movements using the calibrationprocesses described further below. However, when shim structures areused (line 1106), the IMU motion data exhibits a smooth trajectory witha generally constant slope (in FIG. 11 , the C-arm was stabilized withtwo shim structures similar to the shim structure 702 b of FIGS. 7C and7D). The shim structures can also allow the C-arm to move in a generallyconsistent trajectory over multiple rotations, which can make itfeasible to compensate for the off-plane motion using the calibrationprocesses described further below. As shown in FIG. 11 , the shimstructures can help with reducing off-plane motion, but may noteliminate it completely. Any residual off-plane motion can becompensated for via a geometric calibration process, as described ingreater detail below.

FIG. 12 illustrates an example of unwanted movements that may occur atthe second interface 128 during a manual rotation of the imaging arm108. In some instances, the location(s) at which force is applied mayaffect the stability of the imaging arm 108 during manual rotation.Specifically, certain locations may be more likely to produce unwantedand/or non-uniform movements when pushed and/or pulled during manualrotation. For example, when performing a manual propeller rotation, itmay be mechanically advantageous to apply force to the first and secondend portions 114, 116 of the imaging arm 108, since these locations arelocated farther from the center of rotation (also known as the “pivotpoint”), and thus require less force to initiate and/or maintainrotation. However, in situations where the second interface 128 ismechanically unstable (e.g., due to spaces, gaps, or other mechanicallaxity between the base 118 and support arm 120), applying force to thefirst and second end portions 114, 116 of the imaging arm 108 mayproduce greater torque on the second interface 128, which can cause thesupport arm 120 and imaging arm 108 to shift relative to the base 118(e.g., along a translational direction 1202) or otherwise exhibitunwanted and/or non-uniform motions.

In some embodiments, the amount of torque on the second interface 128can be reduced by applying the rotational force to the proximal portion124 of the support arm 120 at or near the second interface 128, ratherthan to the imaging arm 108. However, because this location is closer tothe pivot point, the amount of force to perform a manual propellerrotation may be significantly increased. Additionally, the proximalportion 124 of the support arm 120 may lack handles or grips tofacilitate manual rotation, or the handle at that location may be toosmall to offer sufficient leverage. Accordingly, to reduce the amount offorce for performing a manual propeller rotation at or near the secondinterface 128, the present technology can provide a temporary orpermanent lever structure that attaches to the proximal portion 124 ofthe support arm 120 near the second interface 128 to provide greatermechanical advantage for rotation.

FIGS. 13A-14E illustrate representative examples of lever structuresthat can be used to facilitate manual rotation of an imaging apparatus,in accordance with embodiments of the present technology. Although thelever structures of FIGS. 13A-14E are described and illustrated withreference to components of the imaging apparatus 104 of FIG. 1A, it willbe appreciated that the lever structures can also be used with otherimaging apparatuses and systems. Additionally, any of the features ofthe lever structures of FIGS. 13A-14E can be combined with each other.

FIG. 13A is a partially schematic view of the imaging apparatus 104 witha lever structure 1302 a and FIG. 13B is a closeup, cross-sectional viewof the support arm 120 with the lever structure 1302 a, in accordancewith embodiments of the present technology. The lever structure 1302 ais configured to temporarily or permanently attach to the support arm120 to assist a user in applying a rotational force to the proximalportion 124 of the support arm 120 during a propeller rotation. As bestseen in FIG. 13B, the lever structure 1302 a includes a handle 1304coupled to a clamp 1306. The clamp 1306 can include a pair of clampmembers 1308 connected to a crossbar 1310 in a fixed geometry. The leverstructure 1302 a can have a fork-like configuration in which one end ofthe handle 1304 is coupled to the central portion of the crossbar 1310,and the clamp members 1308 are coupled to the end portions of thecrossbar 1310 and extend longitudinally away from the crossbar 1310.

The handle 1304 can be an elongate rod or shaft configured to be held byone or both of the user's hands. The handle 1304 can be sufficientlylong to provide leverage for rotating the support arm 120 and imagingarm 108. In some embodiments, for example, the handle 1304 has a lengthwithin a range from 10 cm to 70 cm. Optionally, the handle 1304 caninclude texturing, coatings, an ergonomic shape, and/or other suitablefeatures to improve grip. [0141.] The clamp members 1308 can be elongateprongs, arms, etc., configured to secure the lever structure 1302 a tothe proximal portion 124 of the support arm 120 at or near the secondinterface 128. The clamp members 1308 can be configured to fit tightlyaround the support arm 120 so that the lever structure 1302 a does notbecome dislodged when the user applies force to the handle 1304. Forexample, the spacing between the clamp members 1308 can be within arange from 5 cm to 20 cm. The spacing can be identical or similar to thecross-sectional dimension of the proximal portion 124 of the support arm120 to provide a tight fit around the support arm 120. In theillustrated embodiment, the clamp members 1308 are affixed to thecrossbar 1310 at an angle, such that the spacing between the clampmembers 1308 increases with distance from the crossbar 1310. Thisconfiguration can allow the clamp members 1308 to fit snugly around thesupport arm 120 near the pivot point during rotation. Alternatively, theclamp members 1308 can be substantially parallel to each other, suchthat the spacing between the clamp members 1308 is constant. Each clampmember 1308 can have a length within a range from 10 cm to 30 cm, and athickness and/or diameter within a range from 1 cm to 5 cm. The clampmembers 1308 can have any suitable cross-sectional shape (e.g., square,rectangular, circular).

FIG. 13C is a cross-sectional view of the support arm 120 with anadjustable lever structure 1302 b configured in accordance withembodiments of the present technology. The lever structure 1302 b can begenerally similar to the lever structure 1302 a of FIGS. 13A and 13B,except that the lever structure 1302 b includes an adjustable clampmember 1314 that can be moved along the crossbar 1310, and a fixed clampmember 1316 that remains stationary. The adjustable clamp member 1314can be moved relative to the fixed clamp member 1316 to alter the clampspacing, which can allow the clamp 1312 to accommodate different supportarm geometries. In the illustrated embodiment, for example, theadjustable clamp member 1314 is coupled to a trigger 1318 forrepositioning the adjustable clamp member 1314. When the trigger 1318 issqueezed, the adjustable clamp member 1314 can slide along the crossbar1310 toward and/or away from the fixed clamp member 1316. When thetrigger 1318 is released, the adjustable clamp member 1314 can be lockedin place at its current position along the crossbar 1310. Optionally,the clamp 1312 can include teeth, detents, and/or other ratchet-likefeatures so the adjustable clamp member 1314 is movable to a pluralityof different predetermined locations along the crossbar 1310.

FIG. 13D is a cross-sectional view of the support arm 120 with anotheradjustable lever structure 1302 c configured in accordance withembodiments of the present technology. The lever structure 1302 cincludes a handle 1304 coupled to a clamp 1320 (e.g., a C-clamp,G-clamp, U-clamp). The clamp 1320 can include a frame 1322 (e.g., acurved, square, or rectangular bracket) having an adjustable pad 1324 atone end, and a fixed pad 1326 at the other end. The handle 1304 can beconnected to the central portion of the frame 1322 between the two ends.The adjustable pad 1324 can be coupled to a screw 1328 that is rotatableto alter the position of the adjustable pad 1324. Accordingly, the usercan turn the screw 1328 to change the spacing between the adjustable pad1324 and fixed pad 1326 to accommodate different support arm geometries.

FIG. 14A is a partially schematic view of the imaging apparatus 104 witha lever structure 1402 a and FIG. 14B is a front view of the leverstructure 1402 a, in accordance with embodiments of the presenttechnology. Referring first to FIG. 14A, in some embodiments, theimaging apparatus 104 already includes a handle 1404 at or near theproximal portion 124 of the support arm 120 near the second interface128. However, the handle 1404 may be too small to provide sufficientmechanical advantage for manually rotating the support arm 120 andimaging arm 108. Accordingly, the lever structure 1402 a can betemporarily or permanently coupled to the handle 1404 to provide alonger lever arm and/or otherwise increase the mechanical advantage.

Referring next to FIG. 14B, the lever structure 1402 a can include afirst elongate member 1406 (e.g., a rod, shaft, or tube) having a pairof hooks 1408. The hooks 1408 can engage the handle 1404 (FIG. 14A) tosecure the lever structure 1402 a to the support arm 120. The leverstructure 1402 a can also include a second elongate member 1410 (e.g., arod, shaft, or tube) connected to the first elongate member 1406 betweenthe hooks 1408. The second elongate member 1410 can be attached to thefirst elongate member 1406 at a 900 angle or any other suitable angle.During use, the user can grip the first elongate member 1406 and/orsecond elongate member 1410 to apply a rotational force to the supportarm 120 for propeller rotation. In other embodiments, the secondelongate member 1410 can be omitted, such that the user applies forceusing the first elongate member 1406 only.

FIG. 14C is a front view of a lever structure 1402 b configured inaccordance with embodiments of the present technology. The leverstructure 1402 b is identical to the lever structure 1402 a of FIGS. 12Aand 12B, except that the lever structure 1402 b includes a third hook1412 on the second elongate member 1410. The third hook 1412 can furthersecure the lever structure 1402 b to the handle 1404 on the support arm120 (FIG. 14A). It will be appreciated that lever structure 1402 a, 1402b of FIGS. 14A-14C can include any suitable number of hooks (e.g., one,two, three, four, five, or more hooks), and the hooks can be at anysuitable location on the first elongate member 1406 and/or the secondelongate member 1410.

FIGS. 14D and 14E are partially schematic cross-section views of anadjustable lever structure 1402 c coupled to the handle 1404 of theimaging apparatus 104, in accordance with embodiments of the presenttechnology. Although the lever structure 1402 c is depicted as havingtwo hooks 1408 (e.g., similar to the lever structure 1402 a of FIGS. 14Aand 14B), in other embodiments, the lever structure 1402 c can insteadhave three hooks (e.g., similar to the lever structure 1402 b of FIG.14C). Referring first to FIG. 14D, the first elongate member 1406 of thelever structure 1402 c can include a first section 1414 and a secondsection 1416 connected to each other by an adjustable connection 1418.The adjustable connection 1418 can allow the first and second sections1414, 1416 to be moved (e.g., translated) relative to each other alongthe longitudinal axis of the first elongate member 1406. The adjustableconnection 1418 can be any suitable joint or mechanism that permitsmovement of the first section 1414 relative to the second section 1416,such as a slidable mechanism (e.g., a slidable bolt), a screw mechanism(e.g., a threaded bolt), a spring-loaded mechanism, or a combinationthereof.

The first and second sections 1414, 1416 can each include at least onehook 1408, such that the distance between the hooks 1408 can beincreased or decreased by changing the separation between the first andsecond sections 1414, 1416. For example, the hooks 1408 can bepositioned closer together in a retracted configuration (FIG. 14D) wheninitially positioning the lever structure 1402 c on the handle 1404, andcan then be pushed outwards into an extended configuration (FIG. 14E) tocontact and grip the handle 1404. This approach can make it easier toconnect the lever structure 1402 c to the handle 1404, while alsoproviding a tighter fit to prevent the lever structure 1402 c frominadvertently becoming dislodged when force is applied.

In some embodiments, the systems, methods, and devices disclosed hereinreduce or eliminate unwanted movements during manual rotation, asmeasured by some or all of the following metrics: (1) imaging arm motion(e.g., as measured by an IMU or other motion sensor), (2) amount andtype of unwanted motion in the projection images generated by thedetector, (3) image quality of the 3D reconstruction generated from theprojection images, and/or (4) physical distance between the imaging armand the support arm. Each of these metrics is described in detail below.

First, as previously discussed with respect to FIG. 11 , in the absenceof any stabilization, the detector exhibits sudden shifts, oscillations,and/or other unwanted movements. When stabilized with shim structuresand/or by rotation from the support arm, these undesirable movements canbe significantly reduced to produce a relatively smooth andunidirectional rotation of the detector.

Second, in the absence of stabilization, undesirable motions (e.g.,caused by weight shifts and/or flexing of the imaging arm) can be seenin the projection images as a sudden jump in all the structures in thefield of view in the same direction simultaneously. This can indicatethat the center of rotation of the detector was rapidly shifting backand forth, rather than maintaining a single center of rotation, sinceall the structures moved together in the same direction (whereas duringa rotation, there are often structures moving in opposite directionsbased on depth). Further, during and/or after the initial shift, thestructures may reverse direction briefly as the imaging arm movesbackwards with the oscillations. When the imaging arm is stabilizedusing shim structures and/or the other techniques described herein, thesudden jumps in the projection image and/or reversed movements can bereduced or eliminated entirely.

Third, it may be difficult or impossible to generate coherent 3Dreconstructions without using the stabilization techniques describedherein. For example, the unwanted motions of the detector can change thecenter of rotation, thus causing some or all of the structures in the 3Dreconstruction to be misaligned. In some instances, when imaging amarker bead in a phantom, the misalignment can cause the bead to appearas star-like shape in the 3D reconstruction, rather than a coherentspherical shape. Similarly, when imaging a cylindrical phantom withcircular markers, the misalignment can cause the circles to appear asdiscontinuous half-circles in the 3D reconstruction, rather than asingle continuous circle. This misalignment can be reduced or eliminatedby using shim structures and/or rotating from the support arm to improvethe stability of the imaging arm and/or detector during imageacquisition, e.g., in combination with the calibration processesdescribed below.

Fourth, in the absence of shim stabilization, the components of theimaging arm (e.g., the rails) and the support arm (e.g., the distalportion of the support arm) can be displaced by a distance within arange from 1 mm to 5 mm as measured at various angular rotation points.When shim structures are used, it may be nearly impossible for theimaging arm rails to move relative to the support arm since the shimstructures can reduce or prevent the laxity between these components,thus producing a smoother, more uniform motion during image acquisition.

B. Sensors and Methods for Pose Estimation

Referring again to FIG. 1A, as previously discussed, during an mrCBCTprocedure, the imaging arm 108 can be rotated to a plurality ofdifferent angles while the detector 112 obtains 2D images of thepatient's anatomy. In some embodiments, to generate a 3D reconstructionfrom the 2D images, the pose of the imaging arm 108 needs to bedetermined for each image with a high degree of accuracy. However, asdescribed above, a manually-operated imaging apparatus such as a mobileC-arm apparatus may lack the capability to track the pose of the imagingarm 108 with sufficient accuracy for CBCT purposes.

Accordingly, the system 100 can include at least one sensor 154 fortracking the pose of the imaging arm 108 during a manual rotation. Thesensor 154 can be positioned at any suitable location on the imagingapparatus 104. In the illustrated embodiment, for example, the sensor154 is positioned on the detector 112. Alternatively or in combination,the sensor 154 can be positioned at a different location, such as on theradiation source 110, on the imaging arm 108 (e.g., at or near the firstend portion 114, at or near the second end portion 116), on the supportarm 120 (e.g., at or near the distal portion 122, at or near theproximal portion 124), and so on. Additionally, although FIG. 1Aillustrates a single sensor 154, in other embodiments, the system 100can include multiple sensors 154 (e.g., two, three, four, five, or moresensors 154) distributed at various locations on the imaging apparatus104. For example, the system 100 can include a first sensor 154 on thedetector 112, a second sensor 154 on the radiation source 110, etc. Thesensors 154 can be removably coupled or permanently affixed to theimaging apparatus 104.

In some embodiments, because the spatial configuration of the variouscomponents of the imaging apparatus 104 are known, the pose of theimaging arm 108 can be correlated to the pose of other components of theimaging apparatus 104. For example, in embodiments where the detector112 is in a fixed position and orientation with respect to the imagingarm 108, the pose of the detector 112 can be calculated from the pose ofthe imaging arm 108, and vice-versa. Accordingly, any embodimentdescribed herein as using the pose of the imaging arm 108 canalternatively or additionally be adapted to use the pose of the detector112 (or any other suitable component of the imaging apparatus 104).

The sensor 154 can be any sensor type suitable for tracking the pose(e.g., position and/or orientation) of a movable component. For example,the sensor 154 can be configured to track the rotational angle of theimaging arm 108 during a manual propeller rotation. Examples of sensors154 suitable for use with the imaging apparatus 104 include, but are notlimited to, motion sensors (e.g., IMUs, accelerometers, gyroscopes,magnetometers), light and/or radiation sensors (e.g., photodiodes),image sensors (e.g., video cameras), EM sensors (e.g., EM trackers ornavigation systems), shape sensors (e.g., shape sensing fibers orcables), or suitable combinations thereof. In embodiments where thesystem 100 includes multiple sensors 154, the sensors 154 can be thesame or different sensor types. For example, the system 100 can includetwo motion sensors, a motion sensor and a photodiode, a motion sensorand a shape sensor, etc.

In some embodiments, the sensor 154 includes at least one motion sensor,such as a 9-axis IMU having an accelerometer, gyroscope, and/ormagnetometer. The motion sensor can be configured to generate motiondata (e.g., position and/or orientation data over time) as the imagingarm 108 is manually rotated. The motion sensor can be attached to anyportion of the imaging apparatus 104 that undergoes rotation, such asthe detector 112, radiation source 110, imaging arm 108, support arm120, or a combination thereof. In some embodiments, two or more motionsensors are used, with each motion sensor being attached to a differentportion of the imaging apparatus 104 (e.g., a first motion sensor can beattached to the detector 112 and a second motion sensor can be attachedto the radiation source 110).

FIG. 15 is a partially schematic view of a motion sensor 1502 coupled tothe imaging apparatus 104 via an attachment device 1504 configured inaccordance with embodiments of the present technology. The motion sensor1502 is coupled to the attachment device 1504, which in turn is coupledto the detector 112 of the imaging apparatus 104. In the embodiment ofFIG. 15 , the attachment device 1504 is configured to attach to thelateral surface of the detector 112. In other embodiments, however, theattachment device 1504 can be configured to attach to a differentportion of the detector 112, such as the upper surface, lower surface,etc. Optionally the detector 112 and/or the attachment device 1504 caninclude alignment markings (e.g., lines, arrows, or other indicators) toguide the user in placing the attachment device 1504 (and thus, themotion sensor 1502) at a predetermined position and/orientation on thedetector 112.

In the illustrated embodiment, the attachment device 1504 is configuredas a clip or bracket that attaches to the edge of the detector 112 at ornear the lower surface. The clip can include a small,vertically-oriented peg having a short lip or overhanging protrusionthat grips onto the lower edge of the detector 112. Optionally, the clipcan be spring-loaded, can include a rotatable screw, and/or can beotherwise configured to lock into place once positioned at the desiredlocation on the detector 112. In other embodiments, however, theattachment device 1504 can be configured differently. For example, theattachment device 1504 can instead be configured as a container forholding the motion sensor 1502, such as a small rectangular box that canbe placed flat against a flat portion of the detector 112. The containercan include loops, handles, apertures, etc., allowing the container tobe secured to the detector 112 using straps (e.g., straps made of velcroor other adhesive material) and/or other fasteners. Optionally, theattachment device 1504 can be omitted altogether, the motion sensor 1502can instead be coupled directly to the detector 112 via adhesives,fasteners, magnets, straps, etc.

The motion sensor 1502 can generate motion data indicative of the poseof the imaging arm 108. For example, as the imaging arm 108 moves (e.g.,during a manual propeller rotation), the motion sensor 1502 can outputmotion data representing the position and/or orientation (e.g.,rotational angle) of the imaging arm 108 over time. In some embodiments,the motion sensor 1502 generates motion data independently of the imageacquisition performed by the detector 112. Accordingly, in order todetermine the pose of the imaging arm 108 for each image obtained by thedetector 112, the motion data from the motion sensor 1502 can betemporally synchronized or otherwise associated with the images from thedetector 112.

The synchronization can be performed in many different ways. In theillustrated embodiment, for example, the motion sensor 1502 is coupledto a controller 1506 (e.g., an Arduino microcontroller), which in turnis coupled to an image output device 1508. The image output device 1508can receive the images generated by the detector 112 (e.g., in videoformat or any other suitable format). As shown in FIG. 15 , the imagesproduced by the detector 112 can be transmitted to the base 118, and thebase 118 can be coupled to the image output device 1508. In otherembodiments, the detector 112 can be coupled directly to the imageoutput device 1508. The connections between the motion sensor 1502,controller 1506, image output device 1508, detector 112, and base 118can be wired or wireless connections.

The controller 1506 can collect the motion data from the motion sensor1502 in real time and temporally synchronize each image acquired by theimage output device 1508 with the motion data from the motion sensor1502. For example, the controller 1506 can time stamp the motion datareceived from the motion sensor 1502. The controller 1508 can thencompare the time stamps for the motion data to the time stamps on theimage data, and can associate each image with motion data that wasacquired at the same time point or over a similar time period. Thus,each image recorded from the image output device 1508 can be associatedwith a corresponding angle (or a very small range of angles) from themotion sensor 1502.

FIG. 16 is a partially schematic view of a motion sensor 1602 andradiation sensor 1604 attached to the imaging apparatus 104 inaccordance with embodiments of the present technology. The motion sensor1602 (e.g., IMU) and radiation sensor 1604 can be coupled to anattachment device 1606. The attachment device 1606 can be generallysimilar to the attachment device 1504 of FIG. 15 , except that theattachment device 1606 is configured to support both the motion sensor1602 and the radiation sensor 1604. For example, the attachment device1606 can be a clip with a vertically-oriented peg that can betemporarily coupled to the detector 112. The attachment device 1606 canbe mounted on the detector 112 such that the motion sensor 1602 islocated along the lateral surface of the detector 112, while theradiation sensor 1604 protrudes at least partially into the path of theradiation beam output by the detector 112.

The radiation sensor 1604 can be any device capable of detectingexposure to radiation (e.g., x-rays), such as a photodiode. For example,the photodiode can include a scintillator made of silicon-basedmaterials and/or other suitable materials, and can be provided with orwithout a signal amplifier. Accordingly, the radiation sensor 1604 canaccurately measure the time of image acquisition based on exposureradiation passing through the radiation sensor 1604 toward the detector112.

The motion sensor 1602 and radiation sensor 1604 can each be coupled toa controller 1608 (e.g., an Arduino microcontroller) via wired orwireless connections. When the radiation sensor 1604 detects radiation,it can send a signal to the controller 1608 to generate a time stampindicating that an image was acquired. Similarly, the controller 1608can also determine time stamps for the motion data produced by themotion sensor 1602. Accordingly, the image acquisition timing can belinked to the timing of the rotational measurements from the motionsensor 1602, thus allowing each image generated by the detector 112 tobe temporarily synchronized to the corresponding rotational angle of theimaging arm 108.

FIG. 17A is a top view of an attachment device 1702 a, FIG. 17B is aside view of the attachment device 1702 a, and FIG. 17C is a partiallyschematic illustration of the attachment device 1702 a coupled to theimaging apparatus 104, in accordance with embodiments of the presenttechnology. Referring first to FIGS. 17A and 17B together, theattachment device 1702 a is configured to support a motion sensor 1704(e.g., an IMU) and a radiation sensor 1706 (e.g., a photodiode). Theattachment device 1702 a can include a frame 1708 and one or more clips1710 located along the periphery of the frame 1708. Although the frame1708 is depicted as having a circular shape, in other embodiments, theframe 1708 can have a different shape, such as an oval, square,rectangular, or other suitable shape. The frame 1708 can include acentral aperture 1712 to allow radiation to pass through. The frame 1708can also be used to support a fiducial marker grid for a calibrationprocedure, as described in detail further below.

The clips 1710 can be configured to couple the attachment device 1702 ato the detector 112 in a temporary or permanent manner. In someembodiments, the clips 1710 are small, vertically-oriented pegs locatedat the edge of the frame 1708, each having a short lip or overhangingprotrusion to grip onto the edge of the detector 112. As best seen inFIG. 17C, the clips 1710 can secure the attachment device 1702 a to thelower surface of the detector 112, with the frame 1708 located partiallyor entirely out of the radiation path of the detector 112 to avoidattenuating or otherwise interfering with the radiation beam.Optionally, the detector 112, frame 1708, and/or clips 1710 can includealignment markers to guide the user in placing the attachment device1702 a at the appropriate position and/or orientation on the detector112.

In some embodiments, the attachment device 1702 a includes one or moresites along the frame 1708 and/or clips 1710 for attaching the motionsensor 1704 and/or radiation sensor 1706. For example, the motion sensor1704 and radiation sensor 1706 can both be coupled to one of the clips1710, similar to the configuration of the attachment device 1606 of FIG.16 . The motion sensor 1704 can be located along an edge of theattachment device 1702 a away from the path of the radiation beam, whilethe radiation sensor 1706 can protrude at least partially under theframe 1708 and into path of the radiation beam. In other embodiments,however, the motion sensor 1704 and/or radiation sensor 1706 can be atdifferent locations on the attachment device 1702 a. The motion sensor1704 and/or radiation sensor 1706 can each be removably coupled to theattachment device 1702 a or permanently affixed to the attachment device1702 a. The motion sensor 1704 and radiation sensor 1706 can be coupledto other components (e.g., controller, image output device) fortemporally synchronizing the output of the motion sensor 1704 with theimages produced by the detector 112, as discussed above with respect toFIGS. 15 and 16 . Optionally, the radiation sensor 1706 can be omitted,such that the attachment device 1702 a is used to support the motionsensor 1704 only.

FIG. 17D is a side view of an attachment device 1702 b configured inaccordance with embodiments of the present technology. The attachmentdevice 1702 b can be generally similar to the attachment device 1702 aof FIGS. 15A-15C, except that the attachment device 1702 b includes aspring-loaded clip 1714 in place of one or more of the clips 1710. Theclip 1714 can include a spring-loaded protrusion 1716 that can beretracted when positioning the attachment device 1702 b on the detector112. After the attachment device 1702 b is positioned at the desiredlocation, the spring-loaded protrusion 1716 can lock into place aroundthe edge of the detector 112 to secure the frame 1708 to the detector112. The clip 1714 can include a release mechanism (not shown) toretract the spring-loaded protrusion 1716 when removing and/or mountingthe frame 1708. The attachment device 1702 b can optionally beconfigured to support a motion sensor and/or radiation sensor (not shownin FIG. 17D), as discussed above with reference to FIGS. 17A and 17B.The attachment device 1702 b can also be used to support a fiducialmarker grid for a calibration procedure, as described in detail furtherbelow.

FIG. 17E is a side view of an attachment device 1702 c configured inaccordance with embodiments of the present technology. The attachmentdevice 1702 c can be generally similar to the attachment device 1702 aof FIGS. 15A-15C, except that the attachment device 1702 c includes ascrew 1718 in place of one or more of the clips 1710. The screw 1718 canbe in a retracted position when placing the attachment device 1702 c onthe detector 112. After the attachment device 1702 c is positioned atthe desired location, the screw 1718 can be rotated to advance the screw1718 toward the detector 112. The screw 1718 can be advanced until itengages the edge of the detector 112, thus securing the frame 1708 tothe detector 112. To release the attachment device 1702 c, the screw1718 can be rotated in the opposite direction to retract the screw 1718away from the detector 112. The attachment device 1702 c can optionallybe configured to support a motion sensor and/or radiation sensor (notshown in FIG. 17E), as discussed above with reference to FIGS. 17A and17B. The attachment device 1702 c can also be used to support a fiducialmarker grid for a calibration procedure, as described in detail furtherbelow.

Referring again to FIG. 1A, the present technology also provides othertechniques that may be used to estimate the pose of the imaging arm 108,alternatively or in addition to the motion sensor-based techniquesdescribed herein. For example, in some embodiments, the pose of theimaging arm 108 can determined using one or more imaging devices (e.g.,video cameras) positioned around the imaging apparatus 104. In suchembodiments, the system 100 can include one or more fiducial markersplaced at known locations, such as on the patient 102, operating table152, and/or the components of the imaging apparatus 104 (e.g., detector112, radiation source 110, imaging arm 108, and/or support arm 120). Theimaging devices can track the markers as the imaging arm 108 is rotatedto determine the pose of the imaging arm 108.

In another example, the system 100 can include a 3D scanner coupled tothe imaging arm 108. The 3D scanner can be configured to scan areference object (e.g., a block) attached to a fixed location relativeto the imaging arm 108, such as to the operating table 152 and/or thepatient's body. The reference object can have a known geometry, suchthat the pose of the imaging arm 108 can be determined from the pose ofthe reference object within the scans.

As another example, the pose of the imaging arm 108 can be determinedusing shape sensors (e.g., shape-sensing fibers or cables). For example,one portion of a shape-sensing cable can be attached to the operatingtable 152, and another portion to the detector 112. Alternatively or incombination, one or more shape-sensing cables can be attached to otherlocations, such as to the patient 102, radiation source 110, imaging arm108, support arm 120, or suitable combinations thereof. When the imagingarm 108 is rotated, the change in shape of the shape-sensing cable canbe measured and used to calculate the rotational angle of the imagingarm 108.

In a further example, a shape sensor can be carried by a tool within thepatient's body, such as a shape-sensing endoscope. For example, the toolcan output shape data that allows the 3D pose of the tool to beaccurately determined before image acquisition. The pose of the internalshape sensor in each projection image can be used to estimate the poseof the imaging arm 108 when the image was acquired. For example, theactual pose of the tool can be output as a virtual rendering orrepresentation of the 3D shape of the tool inside the patient's body.The pose of the internal shape sensor within the images can beidentified (e.g., using known computer vision and/or image processingtechniques), and registered to the virtual representation of the actualpose. The registration can be used to determine the pose of the imagingarm with respect to the tool and/or the patient's body for each acquiredimage.

In yet another example, an EM sensing system can be used to determinethe pose of the imaging arm 108 during rotation. For example, one ormore EM sensors or trackers can be positioned at various locations, suchas on the patient 102, operating table 152, detector 112, radiationsource 110, imaging arm 108, support arm 120, or suitable combinationsthereof. The position and/orientation of each EM sensor can be trackedand used to estimate the angle of the imaging arm 108. Optionally, an EMsensor can also be carried by a tool within the patient's body, such asan endoscope, biopsy needle, ablation probe, etc. The internal EM sensorcan be used in combination with one or more externally-located EMsensors to perform pose estimation.

In some embodiments, the pose of the imaging arm is estimated using afiducial marker board placed near the patient's body, as an alternativeto or in combination with the other pose estimation techniques describedherein. Conventional fiducial marker boards for intraproceduralimage-based pose estimation (e.g., for tomosynthesis) are typically flatstructures with one or more layers of markers. Conventional fiducialmarker boards are generally unsuitable for imaging techniques involvinga large angular range of rotation such as CBCT because the markers inthe board may not be visible at certain angles due to the limitedvertical height of the board. For example, the markers in a conventionalfiducial marker board may be obscured or disappear entirely from thefield of view when imaged from a lateral angle (e.g., at or near 180°).In contrast, the fiducial marker boards of the present technology canhave a 3D shape in which at least some of the markers lie in differentplanes or are otherwise sufficiently vertically separated so most or allof the markers remain visible over a wide range of imaging angles. Thisallows for estimation of the imaging arm pose over a wide range ofimaging angles. Additionally, conventional fiducial marker boards aregenerally unsuitable for determining the geometric calibrationparameters of the imaging apparatus (e.g., piercing point, pitch, roll,etc.). The fiducial marker boards disclosed herein can be combined witha fiducial marker phantom in order to perform geometric calibration,which can improve the accuracy of the CBCT reconstruction as describedin greater detail below.

FIG. 18A is a side view of a fiducial marker board 1800 for determiningthe pose of an imaging arm, and FIG. 18B is a top view of the fiducialmarker board 1800, in accordance with embodiments of the presenttechnology. The fiducial marker board 1800 can be positioned adjacent ornear a patient's body to provide a reference for estimating a pose of animaging arm. The fiducial marker board 1800 includes a substrate 1802(e.g., a radiolucent material) containing a plurality of fiducialmarkers 1804 (e.g., beads, bearings, flattened disks, etc., made of aradiodense or radiopaque material). The markers 1804 can be arranged ina known geometry (e.g., a grid, pattern, or other spatial configuration)such that when the fiducial marker board 1800 is imaged by an imagingapparatus, the pose of the imaging apparatus (e.g., the angle of theimaging arm) relative to the fiducial marker board 1800 can bedetermined based on the locations of the markers 1804 in the acquiredimages, in accordance with techniques known to those of skill in theart.

As best seen in FIG. 18A, the substrate 1802 can have a non-planar shape(e.g., a curved, semicircular, semioval, and/or U shape) such that atleast some of the markers 1804 are in different planes. In theillustrated embodiment, for example, the substrate 1802 includes a baseregion 1806 and a pair of curved sidewalls 1808 extending upward fromthe base region 1806 by a height H₁. For example, the height H₁ can beat least 1 cm, 2 cm, 5 cm, 10 cm, 15 cm, 20 cm, or 30 cm. In someembodiments, the height H₁ is greater than or equal to theanterior-posterior height of a patient's torso. The height H₁ can besufficiently large such that most or all of the markers 1804 remainvisible even when the fiducial marker board 1800 is imaged from alateral angle (e.g., at or near 1800 relative to the surface of thetable). Accordingly, the fiducial marker board 1800 can be used toestimate the pose of the imaging arm over a wider range of anglescompared to flat fiducial marker boards in which most or all of themarkers lie within a single plane. Optionally, the sidewalls 1808 can bemovably coupled to the base region 1806 (e.g., via a sliding or pivotingconnection) so that the height H₁ can be adjusted, e.g., to accommodatedifferent body sizes and/or imaging setups.

During a medical procedure, the fiducial marker board 1800 can be placedon a operating table with the base region 1806 resting on a surface ofthe table, and the sidewalls 1808 extending upward away from thesurface. A portion of the patient's body (e.g., the patient's torso) canbe positioned on the fiducial marker board 1800 in the cavity formed bythe base region 1806 and sidewalls 1808. A plurality of 2D projectionimages can be acquired while the imaging arm of the imaging apparatus isrotated to a plurality of different angles relative to the patient'sbody and the fiducial marker board 1800. The 2D projection images canthen be analyzed to identify the locations of the markers 1804 in eachimage, e.g., using computer vision algorithms or other suitablealgorithms. Optionally, in embodiments where the markers 1804 are madeof a metallic material, the images can be processed to remove anyimaging artifacts caused by the presence of the metallic material. Theidentified marker locations can be used to estimate the rotational angleof the imaging arm for each image, using techniques known to those ofskill in the art.

FIGS. 18C-18G illustrate additional examples of fiducial marker boards1810-1840 suitable for use with the present technology. The features ofthe fiducial marker boards 1810-1840 can be generally similar to thefeatures of the fiducial marker board 1800 of FIGS. 18A and 18B.Accordingly, the discussion of the fiducial marker boards 1810-1840 ofFIGS. 18C-18G will be limited to those features that differ from theembodiments of FIGS. 18A and 18B. Any of the features of the fiducialmarker boards 1810-1840 can be combined with each other and/or with thefeatures of the fiducial marker board 1800 of FIGS. 18A and 18B.

FIG. 18C is a side view of another fiducial marker board 1810 configuredin accordance with embodiments of the present technology. As shown inFIG. 18C, the markers 1804 in the fiducial marker board 1810 are locatedonly in a portion of the substrate 1802, rather than being distributedthroughout the entirety of the substrate 1802. For example, the markers1804 can be localized to one lateral side or half of the substrate 1802,such that only one of the sidewalls 1808 includes markers 1804. Thisconfiguration can be used, for example, in situations where only asingle side or section of the patient's body is to be imaged (e.g.,during a bronchoscopic procedure performed within a single lung). Insuch situations, the fiducial marker board 1810 can be positioned sothat the markers 1804 are near the side or section of the patient's bodyto be imaged.

FIG. 18D is a side view of yet another fiducial marker board 1820configured in accordance with embodiments of the present technology. Thefiducial marker board 1820 includes a single sidewall 1808, rather thantwo sidewalls 1808. In such embodiments, the base region 1806 can beextended to provide support for the sidewall 1808, such that thefiducial marker board 1820 is J-shaped. Although the base region 1806 isdepicted without any markers 1804, in other embodiments the base region1806 can also include markers 1804. The fiducial marker board 1820 canbe used when imaging a single side or section of the patient's body. Insuch situations, the fiducial marker board 1820 can be positioned sothat the single sidewall 1808 is near the side or section of thepatient's body to be imaged.

FIG. 18E is a side view of a fiducial marker board 1830 configured inaccordance with embodiments of the present technology. The fiducialmarker board 1830 includes a flattened base region 1832 and a pair ofstraight sidewalls 1834. The sidewalls 1834 can be connected to the baseregion 1832 at any suitable angle, such as an angle greater than orequal to 90°, 110°, 120°, 130°, 140°, or 150°. The height H₂ of thesidewalls 1834 can be sufficiently large so that that most or all of themarkers 1804 remain visible even when the fiducial marker board 1830 isimaged from a lateral angle, and can be identical or similar to theheight H₁ of the fiducial marker board 1800 of FIGS. 18A and 18B.Optionally, the sidewalls 1834 can be movably coupled to the base region1832 so the height H₂ can be adjusted, if desired.

Although the fiducial marker board 1830 is illustrated as includingmarkers 1804 throughout the entirety of the substrate 1802, in otherembodiments the fiducial marker board 1830 can include markers 1804 inonly a portion of the substrate 1802 (e.g., similar to the fiducialmarker board 1820 of FIG. 18C). Additionally, although the fiducialmarker board 1830 is shown as having two sidewalls 1834, in otherembodiments the fiducial marker board 1830 can include a single sidewall1834 (e.g., similar to the fiducial marker board 1830 of FIG. 18D).

FIGS. 18F and 18G are side and top views, respectively, of a fiducialmarker board 1840 together with a fiducial marker phantom 1842, inaccordance with embodiments of the present technology. The fiducialmarker board 1840 can be similar to the fiducial marker board 1830 ofFIG. 18E, except that the fiducial marker board 1840 includes a singlesidewall 1834 connected to the base region 1832. The phantom 1842 can betemporarily coupled to the fiducial marker board 1840 via one or morefasteners 1844 (e.g., pegs, screws, magnets, etc.). The phantom 1842 caninclude a respective substrate 1846 (e.g., a radiolucent material)containing a plurality of fiducial markers 1848 (e.g., beads, bearings,flattened disks, etc., made of a radiodense or radiopaque material). Themarkers 1848 can be arranged in a configuration suitable for performinggeometric calibration, as described further below with respect to FIGS.22A-22D.

As best seen in FIG. 18G, the phantom 1842 can be positioned over aportion of the base region 1832 that does not include any markers 1804.In such embodiments, when the fiducial marker board 1840 and phantom1842 are imaged together (e.g., during a geometric calibrationprocedure), the markers 1804 of the fiducial marker board 1840 do notoverlap the markers 1848 of the phantom 1842 in the acquired images, andthus can be identified and distinguished from each other. The use of thephantom 1842 together with the fiducial marker board 1840 for performinggeometric calibration and image acquisition is described in furtherdetail below with respect to FIG. 25A.

C. Methods for Imaging

FIGS. 19-25 illustrate various methods for imaging an anatomic region ofa patient with an imaging apparatus such as a mobile C-arm apparatus.Specifically, FIG. 19 provides a general overview of the imagingprocess, FIGS. 20-22D illustrate methods and devices for calibrating theimaging apparatus, FIGS. 23A and 23B illustrate methods for imageacquisition and reconstruction, FIG. 24 illustrates a method forpreparing the imaging apparatus for imaging, and FIG. 25A illustrates amethod for calibration and imaging using a fiducial marker board. Themethods disclosed herein can be performed using any embodiment of thesystems and devices described herein, such as the system 100 of FIG. 1A.Any of the methods disclosed herein can be performed by an operator(e.g., a physician, nurse, technician, or other healthcareprofessional), by a computing device (e.g., the computing device 130 ofFIG. 1A), or suitable combinations thereof. For example, some processesin a method can be performed manually by an operator, while otherprocesses in the method can be performed automatically orsemi-automatically by one or more processors of a computing device.

FIG. 19 is a flow diagram illustrating a method 1900 for operating animaging apparatus for mrCBCT imaging, in accordance with embodiments ofthe present technology. The method 1900 can be performed with amanually-operated imaging apparatus (e.g., a mobile C-arm apparatus) orany other suitable imaging system or device. The method 1900 begins atblock 1902 with stabilizing the imaging apparatus. As discussed above,mrCBCT imaging can involve stabilizing the imaging apparatus to reduceor prevent undesirable and/or inconsistent movements (e.g.,oscillations, jerks, shifts, flexing, etc.) during manual rotation. Forexample, the imaging arm can be stabilized using one or more shimstructures, such as any of the embodiments described herein with respectto FIGS. 1A and 3A-10D. Alternatively or in combination, the imaging armcan be rotated by applying force to the support arm (e.g., to theproximal portion of the support arm at or near the center of rotation),rather than by applying force to the imaging arm. As previouslydescribed, the force can be applied via one or more lever structurescoupled to the support arm, such as any of the embodiments describedherein with respect to FIGS. 13A-14E. In other embodiments, however, theimaging arm can be manually rotated without any shim structures and/orwithout applying force to the support arm.

Alternatively or in combination, the stabilization process of block 1902can include other processes. For example, block 1902 can also includeadjusting the orbital tilt of the imaging arm to improve weight balanceand/or ensure the detector surface remains close to tangential to thepath of the detector during rotation. Optionally, a motion sensor (e.g.,IMU) can be used to provide feedback about the stability of the imagingarm and/or the effectiveness of specific stabilization steps. Forexample, the feedback can include information characterizing the qualityof the stabilization (e.g., are there residual oscillations, should theshims be repositioned), whether the movement trajectory of the imagingarm was satisfactory (e.g., was there significant tilt during therotation, which may be improved by adjusting the orbital tilt of theC-arm and/or adjusting the shim configuration), and so on. The motionsensor can be attached to any suitable location on the imagingapparatus, such as the detector, radiation source, imaging arm, and/orsupport arm.

At block 1904, the method 1900 continues with calibrating the imagingapparatus. Calibration can be used to compensate for the variations inthe imaging environment and/or mechanical properties of the imagingapparatus that may affect image reconstruction. In some embodiments,calibration includes determining one or more calibration parameters(e.g., distortion correction parameters, geometric calibrationparameters) that are used in the subsequent image acquisition and/orimage reconstruction processes to adjust for the particularcharacteristics of the imaging apparatus. Additional details of methodsand devices suitable for use in the calibration process of block 1904are described below with reference to FIGS. 20-22D.

FIG. 20 is a flow diagram illustrating a method 2000 for calibrating animaging apparatus, in accordance with embodiments of the presenttechnology. The method 2000 can be performed as part of the calibrationprocess of block 1904 of the method 1900 of FIG. 19 . As shown in FIG.20 , the calibration process can be subdivided into two parts:distortion correction (blocks 2002 and 2004) and geometric calibration(blocks 2006 and 2008).

Distortion correction can be performed in embodiments where one or morecomponents of the imaging apparatus (e.g., the detector) are prone toimage distortion that may reduce the accuracy of the subsequent 3Dreconstruction. For example, mobile C-arm apparatuses commonly use animage intensifier as the detector, and the images generated by the imageintensifier can exhibit pincushion and/or barrel distortion, amongothers. The distortion can also change depending on the pose (e.g.,angle) of the image intensifier. Accordingly, the method 2000 caninclude performing a distortion correction process to identify theamount of image distortion at various poses of the imaging arm, anddetermine correction parameters that can be applied to the images toreduce or eliminate distortion. In other embodiments, the distortioncorrection process can be omitted, e.g., if using a flat panel detectorrather than an image intensifier.

At block 2002, the method 2000 can include obtaining one or more firstimages of a first set of fiducial markers (“first fiducial markers”).The first fiducial markers can be radiodense or radiopaque beads,bearings, etc., that are arranged in a known 2D or 3D geometry, such asa grid, array, pattern, shape, etc. The first fiducial markers can becoupled to the detector in a fixed spatial configuration relative to thedetector. The first images can be 2D projection images of the firstfiducial markers acquired by the detector as the imaging arm is manuallyrotated through a plurality of different poses (e.g., rotation angles).Each first image can be associated with a corresponding pose of theimaging arm using any of the devices and techniques described elsewhereherein, such as the embodiments of FIGS. 15-18E.

At block 2004, the method 2000 continues with determining a set ofdistortion correction parameters based on the first images. The firstimages can be transmitted to a computing device (e.g., the computingdevice 130 of FIG. 1A), and the computing device can analyze the firstimages to detect the locations of the first fiducial markers in thefirst images (e.g., using image processing and/or computer visiontechniques known to those of skill in the art). The computing device canthen determine the distortion correction parameters by comparing thelocations of the first fiducial markers in the first images to theknown, true locations of the first fiducial markers on the grid, array,etc. The distortion correction parameters can represent a set oftransformations (e.g., rigid and/or non-rigid transformations such asrotation, translation, deformation, etc.) that would realign the firstfiducial markers in the distorted images to their true locations. Thedistortion correction parameters can be determined through anoptimization process according to techniques known to those of skill inthe art. This process can be performed for each image to determine theappropriate distortion correction parameters for different poses (e.g.,angles) of the imaging arm. The determined distortion correctionparameters can then be applied to each image individually to removedistortion artifacts due to the properties of the detector and/or thepose of the detector, as discussed in greater detail below.

FIG. 21A is a front view of a fiducial marker grid 2102 a configured inaccordance with embodiments of the present technology. The grid 2102 acan be used to determine distortion correction parameters for an imagingapparatus, e.g., as described above with respect to blocks 2002-2004 ofFIG. 20 . The grid 2102 a includes a substrate 2104 containing aplurality of fiducial markers 2106. The substrate 2104 can be made of aradiolucent material, such as acrylonitrile butadiene styrene (ABS),among others. In the illustrated embodiment, the substrate 2104 has acircular shape. In other embodiments, the substrate 2104 can have adifferent shape, such as square, rectangular, oval, etc. The substrate2104 can be sized to fit partially or entirely over the surface of atypical detector. For example, the substrate 2104 can have a diameterand/or width within a range from 9 inches to 12 inches.

The markers 2106 can be beads, bearings, flattened disks, etc., made ofa radiodense or radiopaque material, such as steel or other metallicmaterial. As shown in FIG. 21A, the markers can be arranged in a regular(e.g., square) grid. In some embodiments, the markers 2106 have a size(e.g., diameter and/or width) within a range from 0.5 mm to 3 mm, andare spaced from each other by a distance of 1 cm. In other embodiments,the size and/or arrangement of the markers 2106 can be varied asdesired. The grid 2102 a can include any suitable number of discretemarkers, such as at least 10, 25, 50, 100, 200, 300, 400, 500, 600, 700,800, 900, 1000, or more markers.

During use, the grid 2102 a can be placed adjacent or near the surfaceof the detector so that some or all of the markers 2106 are within thefield of view of the detector. The grid 2102 a can be temporarilycoupled to the detector via clips, brackets, clamps, suction cups,velcro straps, rubber bands, magnets, or any other suitable attachmentmechanism. Optionally, the grid 2102 a and/or detector can include oneor more alignment markers so the grid 2102 a can be coupled to thedetector at a consistent position and/or orientation.

In some embodiments, the grid 2102 a is coupled to an attachment devicethat is connected to the detector. For example, the attachment device1702 a of FIGS. 17A-17E can be used to mount the grid 2102 a to thedetector. In such embodiments, the attachment device 1702 a can becoupled to the detector, and the grid 2102 a can be inserted into orotherwise coupled to the frame 1708 of the attachment device 1702 a.After the distortion correction process has been completed, the grid2102 a can be removed from the frame 1708 while leaving the attachmentdevice 1702 a in place, or the attachment device 1702 a and grid 2102 acan be removed together.

Optionally, the grid 2102 a can include functional components such as amotion sensor (e.g., an IMU) and/or a radiation sensor (e.g., aphotodiode). The motion sensor and radiation detector can be used totrack the pose of the imaging arm and temporally synchronize the posedata to the acquired images, as discussed above. These components can beembedded in or otherwise coupled to the peripheral portion of the grid2102 a to avoid obscuring the field of view of the detector. In otherembodiments, however, the grid 2102 a can be provided without the motionsensor and/or the radiation sensor.

FIGS. 21B-21D are front views of additional fiducial marker grids 2102b-2102 d configured in accordance with embodiments of the presenttechnology. The grids 2102 b-2102 d can be generally similar to the grid2102 a of FIG. 21A. Accordingly, the discussion of the grids 2102 b-2102d will be limited to those features that differ from the grid 2102 a ofFIG. 21A.

Referring first to FIG. 21B, the markers 2106 in the grid 2102 b arearranged so that the central portion 2108 has a different pattern thanthe peripheral portion 2110. This approach can facilitate automatedidentification of the central portion 2108 of the grid 2102 b, which cansimplify the optimization process for calculating the distortioncorrection parameters. In FIG. 21B, for example, the five markers 2106at the central portion 2108 are connected with radiodense or radiopaquelines to form a cross shape. In FIG. 21C, the central marker 2106 at thecentral portion 2108 of the grid 2102 c is spaced apart from the othermarkers 2106 by a known radial distance, so that the central portion2108 has a lower marker density than the peripheral portion 2110. InFIG. 21D, the central portion 2108 of the grid 2102 d includesadditional markers 2106, so that the central portion 2108 has a highermarker density than the peripheral portion 2110. Alternatively or incombination, other types of patterns, shapes, geometries, etc., can beused to distinguish the central portion 2108 from the peripheral portion2110.

Referring again to FIG. 20 , the geometric calibration process of themethod 2000 can include characterizing the geometry of the imagingapparatus during a manual rotation. In some embodiments, geometriccalibration is required because of the mechanical instabilities of theimaging apparatus, which can lead to shifting and/or other non-uniformmotions during rotation as described above. For example, the manualrotation can cause the imaging arm to deviate from the ideal rotationpath (e.g., a single plane, circular rotation path) for CBCT imagingpurposes. Additionally, the components of the imaging apparatus mayshift during manual rotation, e.g., the internal components of thedetector may shift relative to the outer housing. Such internalmovements may be difficult or impossible to detect using anexternally-placed sensor (e.g., an IMU coupled to the detector housing),and thus may require an image-based calibration process. In someembodiments, the changes in geometry during rotation cause theprojection images acquired by the imaging apparatus to be misaligned(e.g., the center of rotation shifts between images), which candetrimentally affect the quality and accuracy of the 3D reconstruction.

Accordingly, the method 2000 can include determining the geometry of theimaging apparatus at various rotational positions in order to determinedeviations and/or other movements that may occur during subsequentrotations. Based on the determined geometry, the method 2000 can computea set of geometric calibration parameters that can be used to adjust theprojection images to compensate for the changes in geometry duringrotation. For example, the geometric calibration parameters canrepresent a set of transformations that, when applied to the projectionimages, corrects any misalignment present in the images due to unwantedmovements of the imaging apparatus.

At block 2006, the method 2000 includes obtaining second images of asecond set of fiducial markers (“second fiducial markers”). The secondfiducial markers can be radiodense or radiopaque beads, bearings, etc.,that are positioned within a phantom in a known 3D configuration. Thesecond images can be 2D projection images acquired by the detector asthe imaging arm is manually rotated to a plurality of different posesrelative to the phantom. In some embodiments, the phantom is positionedat or near the isocenter of the imaging arm, and the imaging arm ismanually rotated around the phantom (e.g., in a propeller rotationdirection) to obtain the second images of the phantom from a pluralityof different rotational angles. Each second image can be associated witha corresponding pose of the imaging arm using any of the devices andtechniques described elsewhere herein, such as the embodiments of FIGS.15-18E. In embodiments where the pose is determined using a fiducialmarker board (e.g., the fiducial marker boards 1800-1830 of FIGS.18A-18E), the phantom can be mounted on or otherwise coupled to thefiducial marker board in a known spatial configuration (e.g., using astand, at a fixed location on the operating table, etc.).

At block 2008, the method 2000 continues with determining a set ofgeometric calibration parameters based on the second images. The secondimages can be transmitted to a computing device (e.g., the computingdevice 130 of FIG. 1A) for analysis. In some embodiments, the computingdevice first corrects any image distortion present in the second imagesusing the distortion correction parameters determined in block 2004. Thecomputing device can then analyze the second images to detect thelocations of the second fiducial markers in the second images (e.g.,using image processing and/or computer vision techniques known to thoseof skill in the art). Subsequently, the computing device can use theimaged locations of the second fiducial markers and the known 3Dconfiguration of the second fiducial markers in the phantom to determinethe geometry of the imaging apparatus during rotation, such as thepiercing point, skewness, pitch, roll, tilt, and/or source-to-detectordistance, among others. For example, the piercing point can representthe center of rotation of the imaging arm and/or the center of thereference coordinate system in the image data. The geometry of theimaging apparatus can be determined using image-based geometriccalibration algorithms known to those of skill in the art.

Subsequently, the geometric calibration parameters can be computed basedon the determined geometry of the imaging apparatus. As discussed above,the geometric calibration parameters can represent a set oftransformations (e.g., rigid and/or non-rigid transformations such asrotation, translation, deformation, etc.) for adjusting the projectionimages at each rotational angle of the imaging apparatus to correct anymisalignment present. For example, if the piercing point of the imagingapparatus shifts for a particular angle of the imaging arm, theprojection image acquired at that angle can be shifted in the oppositedirection to realign the piercing point. The determined geometriccalibration parameters can be applied to each image individually torealign the images in preparation for image reconstruction, as discussedin greater detail below.

FIG. 22A is a perspective view of a fiducial marker phantom 2202 aconfigured in accordance with embodiments of the present technology. Thephantom 2202 a can be used to perform geometric calibration for animaging apparatus, e.g., as described above with respect to blocks2006-2008 of FIG. 20 . The phantom 2202 a includes a substrate 2204containing a plurality of fiducial markers 2206. The substrate 2204 canbe made of a radiolucent material (e.g., ABS) and can be manufacturedusing 3D printing or other suitable techniques. In the illustratedembodiment, the substrate 2204 has an elongated, cylindrical shape. Thesubstrate 2204 can have a length within a range from 7 cm to 25 cm, anda diameter within a range from 7 cm to 25 cm. Optionally, the substrate2204 can be hollow, with a sidewall thickness within a range from 0.5 cmto 5 cm. In other embodiments, however, the geometry (e.g., size, shape)of the substrate 2204 can be varied as desired, e.g., the substrate 2204can be rectangular rather than cylindrical, the substrate 2204 can besolid rather than hollow, etc.

The markers 2206 can be beads, bearings, flattened disks, etc., made ofa radiodense or radiopaque material, such as steel or other metallicmaterial. The markers 2206 can be embedded in the phantom 2202 a atknown spatial locations. In the illustrated embodiment, for example, themarkers 2206 are arranged in two parallel circles at the first end 2208and second end 2210 of the substrate 2204. This arrangement can allowthe piercing point to be automatically identified in images of thephantom 2202 a by connecting diametrically opposed markers 2206 anddetermining the intersection of the connections, in accordance withtechniques known to those of skill in the art. In other embodiments,however, the markers 2206 can be arranged in a different geometry and/orcan be positioned at different locations in the substrate 2204 (e.g.,between the first and second ends 2208, 2210).

FIG. 22B is a perspective view of another fiducial marker phantom 2202 bconfigured in accordance with embodiments of the present technology. Thephantom 2202 b can be generally similar to the phantom 2202 a of FIG.22A, except that the phantom 2202 b includes a central marker 2212representing the piercing point of the imaging apparatus. The centralmarker 2212 can be a bead, bearing, etc., made of a radiodense orradiopaque material, such as copper or another metal. The use of thecentral marker 2212 can be advantageous because it allows the locationof the piercing point to be directly identified in the image data,rather than indirectly calculated from the locations of other markers(e.g., the markers 2206). Although FIG. 22A depicts the phantom 2202 bas including the central marker 2212 together with the markers 2206 atthe first and second ends 2208, 2210, of the substrate 2204, in otherembodiments, the markers 2206 can be omitted such that the centralmarker 2212 is the only marker within the phantom 2202 b.

FIG. 22C is a perspective view of an assembly 2214 that can be used toform the phantom 2202 b, in accordance with embodiments of the presenttechnology. The assembly 2214 includes an elongate shaft 2216 (e.g.,rod, peg, tube, etc.) carrying the central marker 2212. The elongateshaft 2216 can be formed via additive manufacturing (e.g., 3D printing)with a recess for receiving the central marker 2212, or the centralmarker 2212 can be deposited or otherwise formed at the appropriatelocation in the elongate shaft 2216 during the additive manufacturingprocess.

The elongate shaft 2216 can be connected to a first disk 2218 and asecond disk 2220. The first and second disks 2218, 2220 can be locatedat or near the opposite ends of the elongate shaft 2216. The first andsecond disks 2218, 2220 can be integrally formed with the elongate shaft2216 as a single unitary component (e.g., via additive manufacturing).Alternatively, the first and second disks 2218, 2220 can be discretecomponents that are coupled to the elongate shaft 2216 via fasteners,adhesives, bonding, etc. For example, the first and second disks 2218,2220 can each include a central hole, and the ends of the elongate shaft2216 can fit into the holes to form the assembly 2214.

Referring to FIGS. 22B and 22C together, to assemble the phantom 2202 b,the elongate shaft 2216 can be positioned into the hollow interiorcavity of the substrate 2204. The elongate shaft 2216 can have a lengthidentical or similar to the length of the substrate 2204 so that theelongate shaft 2216 extends from the first end 2208 of the substrate2204 to the second end 2210 of the substrate 2204. In embodiments wherethe first and second disks 2218, 2220 are separable from the elongateshaft 2216, the first and second disks 2218, 2220 can then be positionedover the first and second ends 2208, 2210 of the substrate 2204,respectively, and connected to the elongate shaft 2216. The first andsecond disks 2218, 2220 can be sized to partially or fully cover thefirst and second ends 2208, 2210 of the substrate 2204. For example, thefirst and second disks 2218, 2220 can each have a diameter identical orsimilar to the diameter of the first and second ends 2208, 2210,respectively. Optionally, the first and second disks 2218, 2220 can beattached to the substrate 2204 using fasteners (e.g., snaps), adhesives(e.g., tape), or any other suitable technique to ensure that the centralmarker 2212 is positioned at the center of the phantom 2202 b.

FIG. 22D is a perspective view of a fiducial marker phantom 2202 cconfigured in accordance with embodiments of the present technology. Thephantom 2202 c can be generally similar to the phantom 2202 b of FIG.22A, except that the phantom 2202 b includes rings 2222 rather thanindividual markers at the first and second ends 2208, 2210 of thesubstrate 2204. In certain situations, continuous structures such asrings 2222 may be easier to identify in projection images than discretemarkers, which can improve the accuracy of the calibration process. Therings 2222 can be made of a radiodense or radiopaque (e.g., metallic)material. The rings 2222 can have a diameter identical or similar to thediameter of the substrate 2204, and can have a thickness within a rangefrom 1 mm to 5 mm. The rings 2222 can be formed in many different ways.For example, the rings 2222 can be discrete components that are coupledto the substrate 2204 to form the phantom 2202 c. In such embodiments,the first and second ends 2208, 2210 of the substrate 2204 can includegrooves for receiving the rings 2222. Alternatively, the rings 2222 canbe integrally formed with the substrate 2204, such as by using anadditive manufacturing process in which material is deposited into thesubstrate 2204 at the appropriate locations.

Referring again to FIG. 20 , the various steps of the method 2000 can beperformed at different times before and/or during an imaging procedure.For example, the distortion correction process of blocks 2002 and 2004can be performed before an imaging apparatus is used for mrCBCT imagingfor the first time. The distortion correction parameters determined inblock 2004 can be reused for subsequent mrCBCT procedures performedusing the same imaging apparatus, such that the distortion correctionprocess does not need to be performed again. For example, the distortioncorrection parameters can be interpolated or extrapolated to subsequentimages, e.g., using an IMU or other sensor to correlate the storeddistortion correction parameters at a certain angle of rotation to asimilar angle in the subsequent images. In other embodiments, however,the distortion correction process can be performed periodically for thesame imaging apparatus (e.g., once every week, month, six months, year,etc.), performed when there are significant changes in the imaging setup(e.g., if the detector is replaced, if the imaging apparatus is moved toa different environment), or can even be performed each time the imagingapparatus is used. Alternatively, in embodiments where little or noimage distortion is observed (e.g., when a flat panel detector is used),the distortion correction process of blocks 2002 and 2004 can be omittedentirely.

Similarly, the geometric calibration process of blocks 2006 and 2008 canbe performed before an imaging apparatus is used for mrCBCT imaging forthe first time, e.g., after performing distortion correction for theimaging apparatus. The geometric calibration parameters determined inblock 2008 can be reused for subsequent mrCBCT procedures performedusing the same imaging apparatus, such that the geometric calibrationprocess does not need to be performed again. In other embodiments,however, the geometric calibration process can be performed periodicallyfor the same imaging apparatus (e.g., once every week, month, sixmonths, year, etc.), performed when there are significant changes in theimaging setup, or can even be performed each time the imaging apparatusis used (e.g., once before a medical procedure is performed).Optionally, the geometric calibration process of blocks 2006 and 2008may be omitted entirely.

Referring again to FIG. 19 , at block 1906, the method 1900 continueswith acquiring images and generating a 3D reconstruction from theimages. As described elsewhere herein, the process of block 1906 can beused to perform intraprocedural mrCBCT imaging of a target in thepatient anatomy using a manually-operated imaging apparatus that lacksany motors, actuators, etc., for automatically rotating the imaging arm.A representative example of an image acquisition and reconstructionmethod that can be performed as part of the imaging process of block1906 is described below with reference to FIGS. 21A and 21B.

FIG. 23A is a block diagram illustrating a method 2300 for imaging ananatomic region, in accordance with embodiments of the presenttechnology. Some or all of the steps of the method 2300 can be performedas part of the image acquisition and reconstruction process of block1906 of the method 1900 of FIG. 19 . The method 2300 begins at block2302 with manually rotating an imaging arm to a plurality of differentposes. As previously described, the imaging arm can be part of animaging apparatus, such as the imaging apparatus 104 of FIG. 1A. Forexample, the imaging apparatus can be a mobile C-arm apparatus, and theimaging arm can be the C-arm of the mobile C-arm apparatus. The imagingarm can be rotated around a target anatomic region of a patient alongany suitable direction, such as a propeller rotation direction. In someembodiments, the imaging arm is manually rotated to a plurality ofdifferent poses (e.g., angles) relative to the target anatomic region.The imaging arm can be rotated through an arc that is sufficiently largefor performing CBCT imaging. For example, the arc can be at least 90°,100°, 110°, 120°, 130°, 140°, 150°, 160°, 170°, 180°, 190°, 200°, 210°,220°, 230°, 240°, 250°, 260°, 270°, 280°, 290°, 300°, 310°, 320°, 330°,340°, 350°, or 360°.

At block 2304, the method 2300 continues with receiving a plurality ofimages obtained during the manual rotation. The images can be 2Dprojection images generated by a detector (e.g., an image intensifier orflat panel detector) carried by the imaging arm. The method 2300 caninclude generating any suitable number of images, such as at least 50,100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 images. The imagescan be generated at a rate of at least 5 images per second, 10 imagesper second, 20 images per second, 30 images per second, 40 images persecond, 50 images per second, or 60 images per second. In someembodiments, the images are generated while the imaging arm is manuallyrotated through the plurality of different poses, such that some or allof the images are obtained at different poses of the imaging arm.

At block 2306, the method 2300 can include receiving pose data of theimaging arm during the manual rotation. The pose data can be generatedusing any of the techniques and devices described herein. For example,the pose data can be generated based on sensor data from at least onesensor, such as an IMU or another motion sensor coupled to the imagingarm (e.g., to the detector), to the support arm, or a combinationthereof. The sensor data can be processed to determine the pose of theimaging arm at various times during the manual rotation. As previouslydiscussed, the pose of the imaging arm can be estimated without using afiducial marker board or other reference object positioned near thepatient. In other embodiments, however, the pose data can be determinedusing a fiducial marker board, such as the embodiments described abovewith reference to FIGS. 18A-18E. In such embodiments, the fiducialmarker board can be positioned on the operating table at a known spatialconfiguration relative to the imaging apparatus (e.g., the same spatialconfiguration used during calibration).

Optionally, the pose data of block 2306 can also be used to providefeedback to the user on the speed, smoothness, and/or othercharacteristics of the manual rotation. For example, if the imaging armis being rotated too slowly (e.g., if the estimated total rotation timewould take longer than 30 seconds and/or would exceed an automaticshut-off time for the imaging apparatus), then the computing devicecould output an alert (e.g., an image, text, sound, etc.) instructingthe user to increase the rotation speed. Conversely, if the imaging armis being rotated too quickly, the alert could instruct the user to slowdown. As another example, the computing device could display a targetspeed value or range for image acquisition, as well as the actual speedof the imaging arm. The target speed value or range can be based on apredetermined total rotation time for improved image quality, such as arotation time within a range from 1 second to 20 seconds. In someembodiments, a graphical representation of the rotation speed isdisplayed to give the operator real-time feedback during the rotation,e.g., to increase, decrease, or maintain the current rotation speed. Forexample, the representation can show a first indicator when the rotationis at an appropriate speed, a second indicator (e.g. a red indicator)when the speed is too fast, a third indicator (e.g., a green indicator)when the speed is too slow, etc.

At block 2308, the method 2300 includes generating a 3D reconstructionbased on the images received in block 2304 and the pose data received inblock 2306. The 3D reconstruction process can include inputting theimages into an image reconstruction algorithm, such as a filteredbackprojection algorithm, iterative reconstruction algorithm, or othersuitable algorithm known to those of skill in the art. Optionally, theimages can be processed before being input into the algorithm, e.g., byapplying calibration parameters to remove distortion artifacts, correctmisalignment, and/or other adjustments to prepare the images forreconstruction. A representative example of method for generating a 3Dreconstruction is discussed below in connection with FIG. 23B.

FIG. 23B is a flow diagram illustrating a method 2320 for generating a3D reconstruction from a plurality of images, in accordance withembodiments of the present technology. Some or all of the processes ofthe method 2320 can be performed as part of block 2308 of the method2300 of FIG. 23A. The method 2320 begins at block 2312 with associatingeach image with pose data. As discussed above, the pose data can betemporally synchronized with the projection images generated by theimaging apparatus, such that each image is associated with acorresponding pose (e.g., rotational angle) of the imaging arm at ornear the time the image was obtained.

At block 2314, the method 2320 can include applying one or moredistortion correction parameters to some or all of the images. Asdiscussed above, the distortion correction parameters can be applied tothe images in order to reduce or eliminate distortion present in theimages, e.g., due to use of an image intensifier. The distortioncorrection parameters can be parameters that were determined in aprevious calibration process (e.g., the process of block 2004 of FIG. 20). In some embodiments, the distortion correction parameters are storedas a lookup table (or similar data structure) that records a set ofparameters for each angle of the imaging arm. Accordingly, to correctdistortion in a particular image, the angle of the imaging arm at thetime of image acquisition (“target angle”) can be determined using anyof the techniques described herein. The stored distortion correctionparameters corresponding to the target angle can then be retrieved fromthe lookup table. If the target angle does not match any of the entriesin the lookup table, the distortion correction parameters can beinterpolated or extrapolated from other parameters, e.g., the storeddistortion correction parameters for the angle(s) closest to the targetangle.

At block 2316, the method 2320 can include applying one or moregeometric calibration parameters to some or all of the images. Asdiscussed above, the geometric correction parameters can be applied tothe images in order to correct any misalignments present in the images,e.g., due to motions of the imaging arm that deviate from a singleplane, isocentric trajectory. The distortion correction parameters canbe parameters that were determined in a previous calibration process(e.g., the process of block 2008 of FIG. 20 ). In some embodiments, thegeometric calibration parameters are stored as a lookup table (orsimilar data structure) that records a set of parameters for each angleof the imaging arm. Accordingly, when adjusting a particular image, theangle of the imaging arm at the time of image acquisition (“targetangle”) can be determined using any of the techniques described herein.The stored geometric calibration parameters corresponding to the targetangle can then be retrieved from the lookup table. If the target angledoes not match any of the entries in the lookup table, the geometriccalibration parameters can be interpolated or extrapolated from otherparameters, e.g., the stored geometric calibration for the angle(s)closest to the target angle. The geometric calibration parameters cantherefore be used to correct the images in situations where it is notfeasible to use a fiducial marker phantom or other physical calibrationreference.

In some embodiments, the distortion correction parameters of block 2314and/or the geometric calibration parameters of block 2316 are adjustedbased on the pose data of the imaging arm. These adjustments can be madeto account for any deviations from the calibration setup. For example,the actual rotation trajectory of the imaging arm during patient imaging(“imaging trajectory”) can differ from the rotation trajectory of theimaging apparatus when determining the calibration parameters for theimaging apparatus as discussed with respect to FIG. 20 (“calibrationtrajectory”). If the imaging trajectory deviates significantly from thecalibration trajectory, the original parameters may no longer besufficient for correcting image distortion and/or image misalignment.

Accordingly, the method 2320 can further including detecting whether theimaging trajectory deviates significantly from the calibrationtrajectory, e.g., with respect to tilt, pitch, roll, or any othersuitable measurement value. A deviation can be considered significant,for example, if the magnitude of the difference in the value in thecalibration trajectory and the value in the imaging trajectory is atleast 5%, 10%, 15%, 20%, 25%, or 50% of the value in the calibrationtrajectory. The deviations can be detected by comparing the pose data ofthe imaging apparatus during the imaging trajectory (e.g., the pose dataof block 2306 of FIG. 23A) to the pose data of the imaging apparatusduring the calibration trajectory (e.g., the pose data determined duringthe method 2000 of FIG. 20 ).

If significant deviations are detected, the method 2320 can includeupdating or otherwise modifying the distortion correction parametersand/or geometric calibration parameters to account for these deviations.The updates can be made to the distortion correction parameters only, tothe geometric calibration parameters only, or to both sets ofparameters. The updates can be determined based on the pose data of theimaging arm and the known geometry of the imaging apparatus, inaccordance with techniques known to those of skill in the art. Forexample, if the imaging arm exhibited a forward tilt of 1.5° at the 900angular position in the calibration trajectory, but exhibited a forwardtilt of 2.0° at the 900 angular position in the imaging trajectory, thegeometric calibration parameters for the image(s) obtained at or nearthe 900 angular position can be updated to compensate for the differencein the forward tilt. The updated geometric calibration parameters can becomputed by determining how the detected deviation affects the geometryof the imaging apparatus (e.g., with respect to piercing point,skewness, pitch, roll, tilt, and/or source-to-detector distance),determining the amount and/or direction of additional image misalignmentproduced by the change in geometry, and then determining the parametersthat would correct the additional misalignment.

At block 2318, the method 2320 can continue with generating a 3Dreconstruction from the images, in accordance with techniques known tothose of skill in the art. For example, the 3D reconstruction can begenerated using filtered backprojection, iterative reconstruction,and/or other suitable algorithms. Optionally, image interpolation canalso be applied to the reconstruction process to reduce image noisearising from a reduced number of image acquisition angles, ifappropriate.

The method 2320 of FIG. 23B can be modified in many different ways, ifdesired. For example, in other embodiments, block 2314 can be omitted,e.g., if the imaging apparatus uses a flat panel detector or otherwiseis not expected to produce much image distortion. As another example,block 2316 can be omitted, if the images are not expected to besignificantly misaligned. Additionally, the method 2320 can includeother image preprocessing steps not shown in FIG. 23B.

Referring again to FIG. 23A, at block 2310, the method 2300 canoptionally include outputting a graphical representation of the 3Dreconstruction. The graphical representation can be displayed on anoutput device (e.g., the display 132 and/or secondary display 134 ofFIG. 1A) to provide guidance to a user in performing a medicalprocedure. In some embodiments, the graphical representation includesthe 3D reconstruction generated in block 2308, e.g., presented as a 3Dmodel or other virtual rendering. Alternatively or in combination, thegraphical representation can include 2D images derived from the 3Dreconstruction (e.g., 2D axial, coronal, and/or sagittal slices).

In some embodiments, the user views the graphical representation toconfirm whether a medical tool is positioned at a target location. Forexample, the graphical representation can be used to verify whether abiopsy instrument is positioned within a nodule or lesion of interest.As another example, the graphical representation can be used todetermine whether an ablation device is positioned at or near the tissueto be ablated. If the tool is positioned properly, the user can proceedwith performing the medical procedure. If the graphical representationindicates that the tool is not at the target location, the user canreposition the tool, and then repeat some or all of the steps of themethod 2300 to generate a new 3D reconstruction of the tool and/ortarget within the anatomy.

Referring again to FIG. 19 , the method 1900 can optionally includeadditional processes not shown in FIG. 19 . For example, once thecalibration process of block 1904 has been completed, the method 1900can optionally include performing a pre-acquisition rotation of theimaging arm. The pre-acquisition rotation can serve as a “practice”rotation in order to provide feedback to the user on the trajectory andquality of the manual rotation. The feedback can be used to adjust thestabilization, trajectory, speed, quality, and/or other aspects of themanual rotation and/or imaging apparatus setup. In some embodiments,some or all of the processes related to the pre-acquisition rotation areperformed without any radiation to reduce the patient's radiationexposure. A representative example of a method that can be performed aspart of a pre-acquisition process is described below with reference toFIG. 24 .

FIG. 24 is a flow diagram illustrating a method 2400 of preparing animaging apparatus for image acquisition, in accordance with embodimentsof the present technology. The method 2400 can be performed before theimage acquisition and reconstruction process of block 1906 of FIG. 19 .The method 2400 can begin at block 2402, with aligning the field of viewof the imaging apparatus with a target in the anatomic region. In someembodiments, the field of view in the 3D reconstruction is significantlysmaller than the field of view in the projection images. Accordingly,the alignment process of block 2402 can be performed to ensure that thetarget site will be visible in the final CBCT images. In someembodiments, the alignment process is performed after the imagingapparatus has been stabilized and/or calibrated. In other embodiments,however, the alignment process of block 2402 is optional and may beomitted.

In some embodiments, the alignment process of block 2402 includesobtaining one or more test images of the patient anatomy, such as alateral and/or frontal projection image. The computing device can thenprocess the test images to identify the image locations that would bepresent in the image reconstruction. For example, the computing devicecan overlay an indicator (e.g., a circle or other shape, shading,arrows) onto the test images that represents the smaller field of viewof the image reconstruction. As another example, the computing devicecan crop or otherwise remove portions of the test images to removelocations that would not be visible in the image reconstruction.Accordingly, the user can view the processed test images to determinewhether the target will be visible in the image reconstruction. If thetarget will not be visible, the operator can adjust the positioning ofthe imaging apparatus and/or patient, and can acquire new test images.

At block 2404, the method can continue with manually rotating theimaging arm of the imaging apparatus to a plurality of different poses.The manual rotation can be performed under conditions identical orsimilar to the conditions during which the actual image acquisition willtake place. For example, the imaging apparatus can already bestabilized, calibrated, and/or aligned as discussed above. The user canrotate the imaging arm along the rotational trajectory that will be usedto generate the actual images, such as a propeller rotation over a rangeof at least 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, 170°, 180°,190°, 200°, 210°, 220°, 230°, 240°, 250°, 260°, 270°, 280°, 290°, 300°,310°, 320°, 330°, 340°, 350°, or 360°.

At block 2406, the method 2400 continues with receiving pose data of theimaging arm during the manual rotation of block 2404. The pose data canbe generated using any of the devices and techniques described herein.For example, the pose of the imaging arm can be determined using amotion sensor coupled to the imaging arm. The pose data can betransmitted to a suitable computing device (e.g., the computing device130 of FIG. 1A) for storage and processing.

At block 2408, the method 2400 can include comparing the pose data ofblock 2406 to calibration pose data. The calibration pose data caninclude pose data of the imaging arm during a manual rotation performedas part of a previous calibration process (e.g., the geometriccalibration process of FIG. 20 ). The calibration pose data can indicatethe trajectory and/or speed of the imaging arm during the previouscalibration rotation. In some embodiments, the characteristics of themanual rotation performed by the user during the actual imageacquisition should be as close as possible to the characteristics of thecalibration rotation to improve the quality of the image reconstruction.Accordingly, in block 2408, the computing device can analyze the posedata to determine whether the pre-acquisition rotation deviatessignificantly from the calibration rotation with respect to trajectory,speed, stabilization (e.g., absence of oscillations, shifts, or otherunwanted motions), etc.

At block 2410, the method 2400 can include generating feedback and/ormaking adjustments to the imaging apparatus, based on the comparisonperformed in block 2408. For example, the computing device can providefeedback to the user about how the pre-acquisition rotation deviatesfrom the calibration rotation. The computing device can also providerecommendations on how to adjust the rotation and/or imaging apparatusto more closely conform to the calibration rotation or otherwise improvethe operation of the imaging apparatus. For example, if the imagingapparatus was not as well stabilized in the pre-acquisition rotationcompared to the calibration rotation, the user can adjust thestabilization techniques used to improve stability, e.g., by adding moreshim structures, changing the types and/or locations of the shimstructures, altering where force is applied during the rotation, or anyof the other approaches described herein. As another example, if theimaging arm is tilted or otherwise positioned in a way that differs fromthe positioning in the calibration rotation, the computing device canrecommend that the user adjust the imaging arm accordingly. In yetanother example, the feedback can also indicate whether thepre-acquisition rotation was sufficiently smooth, uniform (e.g.,circular), and/or at the appropriate speed for image acquisitionpurposes.

In some embodiments, the computing device can output a graphical userinterface to guide the operator in making the appropriate adjustments.For example, the interface can show a virtual representation of theimaging apparatus with indicators (e.g., arrows) displaying therecommended adjustments. Alternatively or in combination, the interfacecan output textual instructions describing the adjustments to theimaging apparatus and/or rotational trajectory to be made. In someembodiments, the interface displays real-time feedback, such as theactual position and/or orientation of the imaging arm (e.g., from IMUand/or other sensor data) as the user makes adjustments so the user cansee whether the targeted position and/or orientation has been reached.Optionally, the interface can also output alerts, warnings, or otherfeedback during the manual rotation (e.g., “rotation is too fast,”“imaging arm is too far to the left”) so the user can adjust therotation trajectory and/or speed in real-time.

The method 2400 of FIG. 24 can be modified in many different ways, ifdesired. For example, some or all of the processes of the method 2400can be performed multiple times, e.g., to ensure that the user isperforming the manual rotation appropriately and/or that the imagingapparatus is properly set up for acquiring images of the target. In someembodiments, some or all of the processes of blocks 2404, 2406, 2408,and/or 2410 are repeated until the pre-acquisition rotation issufficiently close to the calibration rotation. As another example, theprocess of acquiring and reviewing test images in block 2402 can berepeated until the user confirms that the target is properly aligned forimage reconstruction purposes. Moreover, some or all of the processes ofthe method 2400 can be omitted, such as the processes of blocks 2402and/or 2410.

Referring again to FIG. 19 , the method 1900 can be modified in manydifferent ways. For example, the processes of the method 1900 can beperformed in a different order. In some embodiments, stabilization maynot be necessary to accurately determine the calibration parametersand/or to perform the pre-acquisition rotation. Accordingly, thestabilization process of block 1902 can be performed after thecalibration process of block 1904. Moreover, some of the processes ofthe method 1900 can be optional. For example, any of the processes ofblocks 1902 and/or 1904 can be omitted from the method 1900.

FIG. 25A is a flow diagram illustrating a method 2500 for calibrationand image acquisition using a fiducial marker board, in accordance withembodiments of the present technology. The method 2500 can be generallysimilar to the method 1900 of FIG. 19 , except that a fiducial markerboard is used to estimate the pose (e.g., rotational angle) of theimaging arm during geometric calibration and image acquisition.

The method 2500 begins at block 2502 with attaching a fiducial markerphantom to a fiducial marker board. The fiducial marker phantom can beany of the embodiments described with respect to FIGS. 22A-22D, and thefiducial marker board can be any of the embodiments described withrespect to FIGS. 18A-18G.

At block 2504, the method 2500 can include obtaining a set of firstimages of the fiducial marker phantom and fiducial marker board. Thefirst images can be 2D projection images acquired by the detector as theimaging arm is manually rotated through a plurality of different poses(e.g., rotation angles), as described elsewhere herein. Each first imagecan be associated with a corresponding pose of the imaging arm. The poseof the imaging arm can be determined from the markers of the fiducialmarker board in the first images, as described above with respect toFIGS. 18A-18G.

At block 2506, the method 2500 continues with determining a set ofgeometric calibration parameters based on the first images. Thegeometric calibration parameters can be determined by identifying thelocations of the fiducial markers of the phantom in the first images, asdiscussed above with respect to block 2006 of the method 2000 of FIG. 20. In some embodiments, the combination of the phantom with the fiducialmarker board allows the geometry of the imaging apparatus (e.g.,piercing point, skewness, pitch, roll, tilt, source-to-detectordistance) to be fully determined.

At block 2508, the method 2500 can include removing the fiducial markerphantom from the fiducial marker board and positioning a patient on thefiducial marker board. For example, the patient can be placed in asupine position with their back resting on the board.

At block 2510, the method 2500 continues with obtaining a set of secondimages of the fiducial marker board and the patient. The second imagescan be 2D projection images acquired by the detector as the imaging armis manually rotated through a plurality of different poses (e.g.,rotation angles), as described elsewhere herein. Each second image canbe associated with a corresponding pose of the imaging arm. The pose ofthe imaging arm can be determined from the markers of the fiducialmarker board in the second images, as described above with respect toFIGS. 18A-18G.

At block 2512, the method 2500 can include applying the geometriccalibration parameters to some or all of the second images. The processof block 2512 can be identical or similar to the process of block 2316of the method 2320 of FIG. 23B. For example, in some embodiments, thegeometric calibration parameters of block 2306 are retrieved from alookup table (or similar data structure) based on the pose (e.g.,rotational angle) of the imaging arm, as determined using the fiducialmarker board. Because the same fiducial marker board is used for bothgeometric calibration and image acquisition, the pose estimatesgenerated from the fiducial marker board are consistent across theseprocesses and can therefore be used to determine the appropriategeometric calibration parameters to be applied to each second image.

At block 2514, the method 2500 can include generating a 3Dreconstruction based on the second images. The 3D reconstruction can beproduced from the second images using any of the techniques describedelsewhere herein. Optionally, before the 3D reconstruction is generated,the markers of the fiducial marker board and/or any imaging artifactsproduced by the markers can be subtracted from the second images. Thesubtraction can be performed using computer vision techniques and/orother image processing algorithms known to those of skill in the art.

FIG. 25B is a flow diagram illustrating a method for operating animaging apparatus, in accordance with embodiments of the presenttechnology. At block 2502′, the method 2500′ can include positioning aphantom (e.g., a calibration phantom and/or cylinder) near the imagingapparatus. For example, the phantom can be positioned near an axis ofrotation of an imaging arm of the imaging apparatus. At block 2504′, themethod can include obtaining first 2D images using a shim-stabilizedimaging arm at multiple angles. At block 2506′, the method 2500′ caninclude obtaining pose data of the imaging arm based on the first imagesthat include the phantom. In some embodiments, a general model of thepose of the imaging arm can be created for any arbitrary projectionangle. At block 2508′, the method 2500′ can include removing the phantomfrom the center of rotation and place a fiducial marker board around apatient area of interest. In some embodiments, the fiducial marker boardis an L- or J-shaped fiducial marker board. In other embodiments, thefiducial marker board is not an L- or J-shaped fiducial marker board. Atblock 2510′, the method 2500′ can include obtaining second 2D images ofboth the fiducial marker board and the patient during a rotation of theimaging arm at multiple angles. At block 2512′, the method 2500′ caninclude obtaining second pose data of the imaging arm based on thesecond images. For example, the method 2500′ can include estimating animaging arm angle for each of the second images using the knowngeometric arrangement of the fiducial marker board. The method 2500′ caninclude using the angle estimation from the fiducial marker board toreference the general calibration model generated from the first imagesto determine the imaging arm pose and other relevant geometricinformation for each of the second images. The method 2500′ can includeremoving the signal of the fiducial markers in the fiducial markerboard. At block 2514′, the method 2500′ can include generating a 3Dreconstruction of the image volume using the second images with theestimated pose information determined using the angle estimation fromthe fiducial marker board.

In some embodiments of the present technology, a specialized fiducialboard, such as an L- or J-shaped fiducial marker board or other fiducialmarker board, can be used in conjunction with a phantom (e.g., acalibration phantom and/or cylinder) to perform manually rotated 3Dreconstructions. In such embodiments, the phantom can be configured todetermine the pose of the imaging arm using methods known to thoseskilled in the art. In some embodiments of the methods herein, thephantom can be placed near the center of the imaging arm axis ofrotation and a first series of 2D images is acquired using ashim-stabilized imaging arm at multiple angles. The pose of the imagingarm at each image angle can be determined from the corresponding 2Dimage by tracking and/or segmenting the fiducial markers in the phantomas known to those skilled in the art. Once the pose of the imaging armat each image is determined, a general model of the pose of the imagingarm can be created for any arbitrary projection angle usinginterpolation/extrapolation techniques known to those skilled in theart.

Subsequently, the phantom is removed and a patient area of interest(e.g., a chest) can be placed near the imaging arm (such as theisocenter of a C-arm). A fiducial marker board, such as an L- orJ-shaped fiducial marker board can be placed around the patient near thearea of interest. The fiducial marker board has an arrangement ofradiodense ball bearings or other markers from which the angularposition of the imaging arm can be determined using methods known tothose skilled in the art. A second series of 2D images of both thefiducial marker board and the patient can then be obtained during arotation of the imaging arm at multiple angles. The fiducial markers inthe board can then be automatically tracked and segmented using theirknown pattern. The encoding of the fiducial pattern index allows forestimation of the imaging arm angle for each 2D projection image duringthe second series of images. Once the angle is estimated for each imageof the second series of images, the estimated angle can be used toreference the general calibration model (e.g., a lookup table, etc.)generated from the first series of images. The angle determined fromeach image in the second series of images is thus used to determine thecorrect pose and other relevant geometric information of the C-arm asmodeled from the first series of images. Once the pose of the C-arm isdetermined, then the signals of the fiducial markers in the board can bevirtually (digitally) removed or suppressed from each projection imageusing techniques known to those of skill in the art (e.g. interpolationof pixel neighbors) to limit or prevent metal artifacts within thereconstructed 3D images of the patient. Once the signal from thefiducial markers is removed, a 3D reconstruction can be performed.

FIGS. 26A and 26B are representative CBCT images of a phantom generatedusing a manually-rotated mobile C-arm apparatus. The images wereacquired using a GE Healthcare OEC 9900 C-arm apparatus with an imageintensifier and a rotation angle of approximately 180 degrees. Thephantom was a cylindrical phantom including a set of rings and a centralmarker, similar to the phantom 2202 c of FIG. 22D. The images arecross-section views of the phantom showing the outer edge of thecylinder and the shaft carrying the central marker (the central markeris not shown in the images). The image in FIG. 26A was generated withoutusing calibration or shim stabilization, while the image in FIG. 26B wasgenerated with calibration and shim stabilization, in accordance withembodiments of the present technology. As shown in FIG. 26A, in theabsence of calibration and shim stabilization, the image is blurry,misaligned, and includes significant distortion artifacts. In contrast,after calibration and shim stabilization, the image of FIG. 26Baccurately and clearly depicts the geometry of the phantom.

FIGS. 27A and 27B are representative CBCT images of a lung generatedusing a manually-rotated mobile C-arm apparatus. The images wereacquired using a GE Healthcare OEC 9900 C-arm apparatus with an imageintensifier and a rotation angle of approximately 180°, and show a liveporcine chest with an implanted pulmonary nodule 2702. The image in FIG.27A was generated without using calibration or shim stabilization, whilethe image in FIG. 27B was generated with calibration and shimstabilization, in accordance with embodiments of the present technology.As shown in FIG. 27A, without calibration and shim stabilization, theanatomic structures are not visible in the resulting image. As shown inFIG. 27B, with calibration and shim stabilization, the resulting imagehas sufficiently high spatial resolution and contrast-to-noise ratio toclearly depict the anatomic structures within and near the lung, such asthe nodule 2702 blood vessel 2704, bronchi 2706, and rib 2708.

FIG. 27C is a CBCT image generated using a robotically-rotated CBCTimaging system. Specifically, the image was acquired using a SiemensArtis Zeego CBCT system, a stationary system with a motorized imagingarm, with a rotation angle of approximately 220°. The image shows thesame porcine chest as the images of FIGS. 27A and 27B. As can be seen bycomparing FIGS. 27B and 27C, the imaging techniques described herein canproduce image reconstructions using a manually-operated C-arm apparatusthat are comparable in quality to image reconstructions produced byhigh-end, specialized CBCT systems.

EXAMPLES

The following examples are included to further describe some aspects ofthe present technology, and should not be used to limit the scope of thetechnology.

-   -   1. A method for imaging an anatomic region, the method        comprising:        -   receiving, from a detector carried by an imaging arm of an            x-ray imaging apparatus, a plurality of two-dimensional (2D)            images of the anatomic region, wherein the 2D images are            obtained during manual rotation of the imaging arm, and            wherein the imaging arm is stabilized by a shim structure            during the manual rotation;        -   receiving, from at least one sensor coupled to the imaging            arm, sensor data indicative of a plurality of poses of the            imaging arm during the manual rotation; and        -   generating, based on the 2D images and the sensor data, a 3D            representation of the anatomic region.    -   2. The method of Example 1, wherein the x-ray imaging apparatus        comprises a mobile C-arm apparatus.    -   3. The method of Example 1 or 2, wherein the detector comprises        an image intensifier.    -   4. The method of any one of Examples 1 to 3, wherein the x-ray        imaging apparatus comprises a support arm slidably coupled to        the imaging arm, and the shim structure is positioned at an        interface between the imaging arm and the support arm.    -   5. The method of Example 4, wherein the shim structure is        configured to reduce movement of the imaging arm relative to the        support arm.    -   6. The method of Example 4 or 5, wherein the support arm is        rotatably coupled to a movable base, and the support arm and the        imaging arm are manually rotated relative to the movable base to        obtain the 2D images.    -   7. The method of Example 6, wherein the manual rotation is        actuated by a force applied at or near an interface between the        support arm and the movable base.    -   8. The method of Example 7, wherein the force is applied to a        lever structure coupled at or near the interface between the        support arm and the movable base.    -   9. The method of any one of Examples 4 to 8, wherein the shim        structure comprises at least one elongate member configured to        fit at least partially in the interface between the imaging arm        and the support arm.    -   10. The method of Example 9, wherein the shim structure        includes:    -   a set of elongate members positioned at two sides of the        interface between the imaging arm and the support arm, and a        bridge region connecting the set of elongate members.    -   11. The method of any one of Examples 1 to 10, wherein the        manual rotation comprises a propeller rotation.    -   12. The method of any one of Examples 1 to 11, wherein the        manual rotation comprises a rotation of at least 90 degrees.    -   13. The method of Example 12, wherein the manual rotation        comprises a rotation of at least 180 degrees.    -   14. The method of any one of Examples 1 to 13, wherein the at        least one sensor comprises a motion sensor and the sensor data        comprises motion data of the imaging arm.    -   15. The method of Example 14, wherein the motion sensor        comprises an inertial measurement unit (IMU).    -   16. The method of Example 14 or 15, further comprising        determining the plurality of poses of the imaging arm based on        the motion data.    -   17. The method of any one of Examples 1 to 16, wherein the at        least one sensor includes a sensor coupled to the detector.    -   18. The method of any one of Examples 1 to 17, wherein        generating the 3D representation comprises associating each 2D        image with a corresponding pose of the imaging arm.    -   19. The method of Example 18, wherein associating each 2D image        with the corresponding pose comprises identifying a pose of the        imaging arm when the 2D image was obtained.    -   20. The method of any one of Examples 1 to 19, further        comprising applying one or more distortion correction parameters        to at least some of the 2D images before generating the 3D        representation.    -   21. The method of any one of Examples 1 to 20, further        comprising applying one or more geometric calibration parameters        to at least some of the 2D images before generating the 3D        representation.    -   22. The method of any one of Examples 1 to 21, further        comprising outputting real-time feedback to an operator during        the manual rotation for adjusting a rotation speed of the        imaging arm.    -   23. The method of any one of Examples 1 to 22, further        comprising outputting the 3D representation on a graphical user        interface during a medical procedure performed in the anatomic        region.    -   24. A system for imaging an anatomic region, the system        comprising:    -   a shim structure configured to stabilize manual rotation of an        imaging arm of an x-ray imaging apparatus;    -   at least one sensor configured to generate sensor data        indicative of a pose of the imaging arm;    -   one or more processors operably coupled to the x-ray imaging        apparatus and the at least one sensor; and    -   a memory operably coupled to the one or more processors and        storing instructions that, when executed by the one or more        processors, cause the system to perform operations comprising:    -   receiving, from the x-ray imaging apparatus, a sequence of        two-dimensional (2D) images of the anatomic region obtained        during the manual rotation of the imaging arm;    -   determining, based on the sensor data, pose information of the        imaging arm during the manual rotation of the imaging arm; and    -   generating, based on the 2D images and the pose information, a        3D reconstruction of the anatomic region.    -   25. The system of Example 24, wherein the x-ray imaging        apparatus comprises a mobile C-arm apparatus.    -   26. The system of Example 24 or 25, wherein the x-ray imaging        apparatus comprises a support arm slidably coupled to the        imaging arm, and the shim structure is configured to be        positioned at an interface between the imaging arm and the        support arm.    -   27. The system of Example 26, wherein the shim structure is        configured to reduce movement of the imaging arm relative to the        support arm.    -   28. The system of Example 27, wherein the shim structure        inhibits orbital rotation of the imaging arm.    -   29. The system of any one of Examples 26 to 28, wherein the        support arm is rotatably coupled to a movable base, and the        support arm and the imaging arm are manually rotated relative to        the movable base to obtain the 2D images.    -   30. The system of Example 29, further comprising a lever        structure coupled at or near an interface between the support        arm and the movable base, wherein the lever structure is        configured to facilitate the manual rotation of the imaging arm.    -   31. The system of any one of Examples 26 to 30, wherein the shim        structure comprises at least one elongate member configured to        fit at least partially in the interface between the imaging arm        and the support arm.    -   32. The system of Example 31, wherein the shim structure        includes a pair of arm regions positioned at two sides of the        interface between the imaging arm and the support arm.    -   33. The system of Example 32, wherein the shim structure        includes a bridge region connecting the pair of arm regions.    -   34. The system of any one of Examples 24 to 33, wherein the        manual rotation comprises an angular rotation.    -   35. The system of any one of Examples 24 to 34, wherein the        manual rotation comprises a rotation of at least 90 degrees.    -   36. The system of any one of Examples 24 to 35, wherein the at        least one sensor comprises a motion sensor and the sensor data        comprises motion data of the imaging arm.    -   37. The system of Example 36, wherein the motion sensor        comprises an inertial measurement unit (IMU).    -   38. The system of Example 36 or 37, wherein the motion sensor is        coupled to the detector.    -   39. The system of Example 38, wherein the motion sensor is        coupled to the detector via an attachment device.    -   40. The system of Example 39, wherein the attachment device        comprises a clip, bracket, frame, or container.    -   41. The system of any one of Examples 24 to 40, further        comprising a controller operably coupled to the at least one        sensor, wherein the controller is configured to temporally        synchronize the 2D images to the sensor data generated by the at        least one sensor.    -   42. The system of any one of Examples 24 to 41, further        comprising a radiation sensor configured to generate a signal in        response to detected radiation, wherein the signal is        transmitted to the controller to temporally synchronize the 2D        images to the sensor data.    -   43. The system of any one of Examples 24 to 42, further        comprising a display configured to output a graphical        representation of the 3D reconstruction.    -   44. A non-transitory computer-readable medium comprising        instructions that, when executed by one or more processors of a        computing system, cause the computing system to perform        operations comprising:    -   receiving, from a detector carried by an imaging arm of a mobile        C-arm apparatus, a plurality of projection images of an anatomic        target, wherein the projection images are obtained during manual        rotation of the imaging arm, and wherein the imaging arm is        stabilized by a shim structure during the manual rotation;    -   receiving, from at least one sensor coupled to the imaging arm,        pose data of the imaging arm during the manual rotation; and    -   generating, based on the projection images and the pose data, a        3D reconstruction of the anatomic target.    -   45. A method for imaging an anatomic region, the method        comprising:    -   receiving, from a detector carried by an imaging arm of an x-ray        imaging apparatus, a plurality of two-dimensional (2D) images of        the anatomic region, wherein the 2D images are obtained during        manual rotation of the imaging arm, and wherein the imaging arm        is stabilized by a shim structure during the manual rotation;    -   receiving pose data of the imaging arm during the manual        rotation; and    -   generating, based on the 2D images and the pose data, a 3D        representation of the anatomic region.    -   46. The method of Example 45, wherein the pose data is generated        from images of a fiducial marker board positioned near the        anatomic target.    -   47. The method of Example 46, wherein the fiducial marker board        includes a plurality of fiducial markers and at least some of        the fiducial markers are located in different planes.    -   48. The method of Example 46 or 47, wherein the fiducial marker        board includes a base region and at least one sidewall extending        upward from the base region.    -   49. The method of any one of Examples 45 to 48, wherein the pose        data is generated by at least one sensor coupled to the imaging        arm.    -   50. A method for operating an imaging apparatus, the method        comprising:    -   receiving, from a detector carried by an imaging arm of the        imaging apparatus, a plurality of first images of a set of first        fiducial markers, wherein the first images are obtained during        manual rotation of the imaging arm;    -   determining a set of distortion correction parameters for the        imaging apparatus based on the first images;    -   receiving, from the detector, a plurality of second images of a        set of second fiducial markers, wherein the second images are        obtained during manual rotation of the imaging arm; and    -   determining a set of geometric calibration parameters for the        imaging apparatus based on the second images.    -   51. The method of Example 50, wherein the imaging apparatus is a        mobile C-arm apparatus.    -   52. The method of Example 50 or 51, wherein the first and second        images are each obtained during a propeller rotation of the        imaging arm.    -   53. The method of any one of Examples 50 to 52, wherein the        detector comprises an image intensifier.    -   54. The method of any one of Examples 50 to 53, wherein the        first fiducial markers are arranged in a grid.    -   55. The method of any one of Examples 50 to 54, further        comprising determining, using at least one sensor carried by the        imaging arm, pose data of the imaging arm associated with the        first images, wherein the distortion correction parameters are        determined based on the pose data.    -   56. The method of any one of Examples 50 to 55, wherein the        second fiducial markers are disposed within a phantom.    -   57. The method of any one of Examples 50 to 56, further        comprising adjusting at least some of the second images using        the set of distortion correction parameters.    -   58. The method of any one of Examples 50 to 57, further        comprising determining, using at least one sensor carried by the        imaging arm, pose data of the imaging arm associated with the        second images, wherein the geometric calibration parameters are        determined based on the pose data.    -   59. The method of Example 58, further comprising processing the        second images to determine one or more of the following:        piercing point, skewness, pitch, roll, tilt, or        source-to-detector distance of the imaging apparatus.    -   60. The method of Example 58 or 59, further comprising:    -   receiving, from at least one sensor coupled to the imaging arm,        second pose data of the imaging arm during a pre-acquisition        manual rotation;    -   comparing the second pose data to the pose data associated with        the second images; and outputting feedback to a user based on        the comparison.    -   61. The method of Example 60, wherein the feedback comprises        feedback regarding one or more of the following: rotation        trajectory, rotation speed, orientation of the imaging arm,        position of the imaging arm, or stability of the imaging arm.    -   62. The method of any one of Examples 50 to 61, further        comprising:    -   receiving, from the detector, a plurality of third images of an        anatomic region of a patient, wherein the third images are        obtained during manual rotation of the imaging arm, and wherein        the imaging arm is stabilized by a shim structure during the        manual rotation;    -   receiving, from at least one sensor coupled to the imaging arm,        pose data of the imaging arm associated with the third images;        and generating a volumetric reconstruction of the anatomic        region based on the third images and the pose data.    -   63. The method of Example 62, further comprising:    -   applying the distortion correction parameters to the third        images; and applying the geometric calibration parameters to the        third images.    -   64. The method of Example 63, further comprising updating one or        more of the distortion correction parameters or the geometric        calibration parameters based on data from the at least one        sensor, before generating the volumetric reconstruction.    -   65. A system for imaging an anatomic region, the system        comprising:    -   one or more processors; and    -   a memory operably coupled to the one or more processors and        storing instructions that, when executed by the one or more        processors, cause the system to perform operations comprising:    -   receiving, from a detector carried by an imaging arm of an x-ray        imaging apparatus, a plurality of first images of a fiducial        marker grid, wherein the first images are obtained during manual        rotation of the imaging arm;    -   determining a set of distortion correction parameters for the        imaging apparatus based on the first images;    -   receiving, from the detector, a plurality of second images of a        fiducial marker phantom, wherein the second images are obtained        during manual rotation of the imaging arm; and    -   determining a set of geometric calibration parameters for the        imaging apparatus based on the second images.    -   66. The system of Example 65, wherein the x-ray imaging        apparatus is a mobile C-arm apparatus.    -   67. The system of Example 65 or 66, wherein the first and second        images are each obtained during a propeller rotation of the        imaging arm.    -   68. The system of any one of Examples 65 to 67, wherein the        detector comprises an image intensifier.    -   69. The system of any one of Examples 65 to 68, further        comprising the fiducial marker grid.    -   70. The system of Example 69, wherein the fiducial marker grid        includes a central portion and a peripheral portion, the central        portion having a different pattern than the peripheral portion.    -   71. The system of any one of Examples 65 to 70, further        comprising an attachment device for mounting the fiducial marker        grid to the detector.    -   72. The system of Example 71, further comprising a motion        sensor, wherein the attachment device is configured to couple        the motion sensor to the detector.    -   73. The system of any one of Examples 65 to 72, wherein the        operations further comprise determining, using the motion        sensor, pose data of the imaging arm associated with the first        images, wherein the distortion correction parameters are        determined based on the pose data.    -   74. The system of any one of Examples 65 to 73, further        comprising the fiducial marker phantom.    -   75. The system of Example 74, wherein the fiducial marker        phantom includes at least one second fiducial marker at a        central portion of the phantom.    -   76. The system of Example 74 or 75, wherein the phantom        includes:    -   a first ring at a first end of the phantom; and    -   a second ring at a second end of the phantom opposite the first        end.    -   77. The system of any one of Examples 65 to 76, wherein the        operations further comprise adjusting at least some of the        second images using the set of distortion correction parameters.    -   78. The system of any one of Examples 65 to 77, further        comprising a motion sensor coupled to the detector.    -   79. The system of Example 78, wherein the operations further        comprise determining, using the motion sensor, pose data of the        imaging arm associated with the second images, wherein the        geometric calibration parameters are determined based on the        pose data.    -   80. The system of Example 79, wherein the operations further        comprise:    -   receiving, from the motion sensor, second pose data of the        imaging arm during a pre-acquisition manual rotation; and    -   comparing the second pose data to the pose data associated with        the second images.    -   81. The system of Example 80, further comprising a display        configured to output feedback to a user based on the comparison        of the second pose data to the pose data, wherein the feedback        comprises feedback regarding one or more of the following:        rotation trajectory, rotation speed, orientation of the imaging        arm, position of the imaging arm, or stability of the imaging        arm.    -   82. The system of any one of Examples 65 to 81, wherein the        operations further comprise:    -   receiving, from the detector, a plurality of third images of an        anatomic region of a patient, wherein the third images are        obtained during manual rotation of the imaging arm, and wherein        the imaging arm is stabilized by a shim structure during the        manual rotation;    -   receiving, from a motion sensor coupled to the detector, pose        data of the imaging arm associated with the third images;    -   adjusting the third images using the distortion correction        parameters;    -   adjusting the third images using the geometric calibration        parameters; and    -   generating a volumetric reconstruction of the anatomic region        based on the third images and the pose data.    -   83. A non-transitory computer-readable medium comprising        instructions that, when executed by one or more processors of a        computing system, cause the computing system to perform        operations comprising:    -   receiving, from a detector carried by an imaging arm of an        imaging apparatus, a plurality of first images of a set of first        fiducial markers, wherein the first images are obtained during        manual rotation of the imaging arm;    -   determining a set of distortion correction parameters for the        imaging apparatus based on the first images;    -   receiving, from the detector, a plurality of second images of a        set of second fiducial markers, wherein the second images are        obtained during manual rotation of the imaging arm; and    -   determining a set of geometric calibration parameters for the        imaging apparatus based on the second images.    -   84. A method for imaging an anatomic region, the method        comprising:    -   receiving, from a detector carried by an imaging arm of a mobile        C-arm apparatus, a plurality of 2D images of the anatomic        region, wherein the 2D images are obtained during manual        rotation of the imaging arm, and wherein the imaging arm is        stabilized by a shim structure during the manual rotation;    -   receiving data indicative of a plurality of poses of the imaging        arm during the manual rotation; and    -   generating, based on the 2D images and the data, a 3D        reconstruction of the anatomic region.    -   85. The method of Example 84, wherein the mobile C-arm apparatus        comprises a support arm slidably coupled to the imaging arm, and        the shim structure is positioned at an interface between the        imaging arm and the support arm.    -   86. The method of Example 85, wherein the shim structure is        configured to reduce movement of the imaging arm relative to the        support arm.    -   87. The method of Example 84 or Example 85, wherein the shim        structure is configured to fit at least partially in the        interface between the imaging arm and the support arm.    -   88. The method of Example 87, wherein the shim structure        includes:    -   a pair of arm regions configured to be positioned at two sides        of the interface between the imaging arm and the support arm,        and    -   a bridge region connecting the set of elongate members.    -   89. The method of Example 85, wherein the support arm is        rotatably coupled to a movable base, and the support arm and the        imaging arm are manually rotated relative to the movable base to        obtain the 2D images.    -   90. The method of Example 89, wherein the manual rotation is        actuated by a force applied to a lever structure coupled at or        near an interface between the support arm and the movable base.    -   91. The method of any one of Examples 84 to 90, wherein the        manual rotation comprises a propeller rotation.    -   92. The method of any one of Examples 84 to 91, wherein the        manual rotation comprises a rotation of at least 90 degrees.    -   93. The method of any one of Examples 84 to 91, wherein the data        indicative of the plurality of poses of the imaging arm are        received from a motion sensor coupled to the imaging arm.    -   94. The method of Example 93, wherein the motion sensor        comprises an inertial measurement unit.    -   95. The method of any one of Examples 84 to 94, wherein the        plurality of 2D images includes a fiducial board, and wherein        the data indicative of the plurality of poses of the imaging arm        are generated from the 2D images.    -   96. The method of any one of Examples 84 to 95, further        comprising associating each 2D image with a corresponding pose        of the imaging arm at a time when the 2D image was obtained.    -   97. The method of any one of Examples 84 to 96, wherein the 3D        reconstruction comprises a cone-beam computed tomography        reconstruction.    -   98. The method of any one of Examples 84 to 97, further        comprising applying one or more distortion correction parameters        to at least some of the 2D images before generating the 3D        reconstruction.    -   99. The method of any one of Examples 84 to 98, further        comprising applying one or more geometric calibration parameters        to at least some of the 2D images before generating the 3D        reconstruction.    -   100. The method of any one of Examples 84 to 99, wherein        generating the 3D reconstruction is based on pose data        previously acquired using the imaging arm.    -   101. A method for imaging an anatomic region, the method        comprising:    -   receiving, from a detector carried by an imaging arm of an x-ray        imaging apparatus, a plurality of 2D images of an anatomic        region, wherein the 2D images are obtained during manual        rotation of the imaging arm, and wherein the imaging arm is        coupled to a shim structure during the manual rotation;    -   receiving pose data of the imaging arm during the manual        rotation; and    -   generating, based on the 2D images and the pose data, a 3D        representation of the anatomic region.    -   102. The method of Example 101, wherein the x-ray imaging        apparatus is a mobile C-arm apparatus.    -   103. The method of Example 101 or Example 102, wherein the        manual rotation comprises a propeller rotation of at least 180        degrees.    -   104. The method of any one of Examples 101 to 103, wherein the        shim structure inhibits orbital rotation of the imaging arm.    -   105. The method of any one of Examples 101 to 104, wherein the        x-ray imaging apparatus comprises a support arm coupled to the        imaging arm, and the shim structure is configured to inhibit        movement of the imaging arm relative to the support arm.    -   106. The method of Example 105, wherein the shim structure is        configured to fill at least one gap in an interface between the        support arm and the imaging arm.    -   107. The method of Example 106, wherein the shim structure        comprises at least one elongate member configured to be        positioned within the at least one gap.    -   108. The method of any one of Examples 101 to 107, wherein the        pose data is received from at least one sensor associated with        the x-ray imaging apparatus, and wherein the at least one sensor        comprises a motion sensor coupled to the imaging arm.    -   109. The method of any one of Examples 101 to 108, further        comprising temporally synchronizing the 2D images to the pose        data.    -   110. The method of any one of Examples 101 to 109, wherein        temporally synchronizing the 2D images to the pose data        comprises identifying a pose of the imaging arm at a time when        each 2D image was obtained.    -   111. The method of Example 110, wherein the pose comprises a        rotation angle of the imaging arm.    -   112. The method of any one of Examples 101 to 111, wherein the        pose data is second pose data and generating the 3D        reconstruction is based on first pose data previously acquired        using the imaging arm.    -   113. A method for imaging an anatomic region, the method        comprising:    -   receiving, from a detector carried by an imaging arm of a mobile        C-arm apparatus, a plurality of 2D projection images of the        anatomic region, wherein the 2D projection images are obtained        during manual rotation of the imaging arm, and wherein the        imaging arm is mechanically stabilized by a shim structure        during the manual rotation;    -   determining a plurality of rotation angles of the imaging arm        during the manual rotation, wherein each rotation angle is        associated with a corresponding 2D projection image;    -   generating, based on the 2D projection images and the associated        rotation angles, a 3D reconstruction of the anatomic region; and    -   outputting the 3D reconstruction on a graphical user interface        configured to provide guidance during a medical procedure        performed in the anatomic region.

CONCLUSION

Although many of the embodiments are described above with respect tosystems, devices, and methods for performing a medical procedure in apatient's lungs, the technology is applicable to other applicationsand/or other approaches, such as medical procedures performed in otheranatomic regions (e.g., the musculoskeletal system). Moreover, otherembodiments in addition to those described herein are within the scopeof the technology. Additionally, several other embodiments of thetechnology can have different configurations, components, or proceduresthan those described herein. A person of ordinary skill in the art,therefore, will accordingly understand that the technology can haveother embodiments with additional elements, or the technology can haveother embodiments without several of the features shown and describedabove with reference to FIGS. 1A-27C.

The various processes described herein can be partially or fullyimplemented using program code including instructions executable by oneor more processors of a computing system for implementing specificlogical functions or steps in the process. The program code can bestored on any type of computer-readable medium, such as a storage deviceincluding a disk or hard drive. Computer-readable media containing code,or portions of code, can include any appropriate media known in the art,such as non-transitory computer-readable storage media.Computer-readable media can include volatile and non-volatile, removableand non-removable media implemented in any method or technology forstorage and/or transmission of information, including, but not limitedto, random-access memory (RAM), read-only memory (ROM), electricallyerasable programmable read-only memory (EEPROM), flash memory, or othermemory technology; compact disc read-only memory (CD-ROM), digital videodisc (DVD), or other optical storage; magnetic cassettes, magnetic tape,magnetic disk storage, or other magnetic storage devices; solid statedrives (SSD) or other solid state storage devices; or any other mediumwhich can be used to store the desired information and which can beaccessed by a system device.

The descriptions of embodiments of the technology are not intended to beexhaustive or to limit the technology to the precise form disclosedabove. Where the context permits, singular or plural terms may alsoinclude the plural or singular term, respectively. Although specificembodiments of, and examples for, the technology are described above forillustrative purposes, various equivalent modifications are possiblewithin the scope of the technology, as those skilled in the relevant artwill recognize. For example, while steps are presented in a given order,alternative embodiments may perform steps in a different order. Thevarious embodiments described herein may also be combined to providefurther embodiments.

As used herein, the terms “generally,” “substantially,” “about,” andsimilar terms are used as terms of approximation and not as terms ofdegree, and are intended to account for the inherent variations inmeasured or calculated values that would be recognized by those ofordinary skill in the art.

Moreover, unless the word “or” is expressly limited to mean only asingle item exclusive from the other items in reference to a list of twoor more items, then the use of “or” in such a list is to be interpretedas including (a) any single item in the list, (b) all of the items inthe list, or (c) any combination of the items in the list. Additionally,the term “comprising” is used throughout to mean including at least therecited feature(s) such that any greater number of the same featureand/or additional types of other features are not precluded. As usedherein, the phrase “and/or” as in “A and/or B” refers to A alone, Balone, and A and B.

To the extent any materials incorporated herein by reference conflictwith the present disclosure, the present disclosure controls.

It will also be appreciated that specific embodiments have beendescribed herein for purposes of illustration, but that variousmodifications may be made without deviating from the technology.Further, while advantages associated with certain embodiments of thetechnology have been described in the context of those embodiments,other embodiments may also exhibit such advantages, and not allembodiments need necessarily exhibit such advantages to fall within thescope of the technology. Accordingly, the disclosure and associatedtechnology can encompass other embodiments not expressly shown ordescribed herein.

1. (canceled)
 2. A method for operating a mobile C-arm apparatus, themethod comprising: receiving, from a detector carried by an imaging armof the mobile C-arm apparatus, a plurality of first images of a set offiducial markers, wherein the first images are obtained during manualrotation of the imaging arm, wherein the mobile C-arm apparatuscomprises a support arm movably coupled to the imaging arm, and whereinmovement of the imaging arm relative to the support arm is constrainedby a stabilization mechanism during the manual rotation; determining aset of geometric calibration parameters for the mobile C-arm apparatusbased on the first images; and generating a 3D reconstruction of ananatomic region of a patient based on a plurality of second images ofthe anatomic region and the geometric calibration parameters.
 3. Themethod of claim 2, further comprising: before receiving the plurality offirst images, receiving a plurality of third images of a set of fiducialmarkers, wherein the third images are obtained during manual rotation ofthe imaging arm, and wherein movement of the imaging arm relative to thesupport arm is constrained by the stabilization mechanism during theobtaining of the third images; and determining a set of distortioncorrection parameters for the mobile C-arm apparatus based on the thirdimages, wherein the 3D reconstruction is generated based on thedistortion correction parameters.
 4. The method of claim 2, wherein thestabilization mechanism comprises a shim structure.
 5. The method ofclaim 2, wherein the stabilization mechanism comprises: a pair of armregions; and a bridge region connecting the pair of arm regions.
 6. Themethod of claim 2, wherein the stabilization mechanism is configured tofill at least one gap in an interface between the imaging arm and thesupport arm.
 7. The method of claim 2, wherein the first images areobtained during a propeller rotation of the imaging arm.
 8. The methodof claim 2, wherein the fiducial markers are arranged in a grid.
 9. Themethod of claim 2, wherein the fiducial markers are disposed within aphantom.
 10. The method of claim 2, further comprising determining,using at least one sensor coupled to the imaging arm, data indicative ofa plurality of poses of the imaging arm during the manual rotation,wherein the geometric calibration parameters are determined based on thedata.
 11. The method of claim 10, further comprising: receiving, fromthe at least one sensor coupled to the imaging arm, data indicative of aplurality of second poses of the imaging arm during a pre-acquisitionmanual rotation; comparing the data indicative of the plurality ofsecond poses to the data indicative of the plurality of poses; andoutputting feedback to a user based on the comparison.
 12. The method ofclaim 11, wherein the feedback comprises feedback regarding one or moreof the following: rotation trajectory, rotation speed, orientation ofthe imaging arm, position of the imaging arm, or stability of theimaging arm.
 13. The method of claim 2, wherein the geometriccalibration parameters comprise one or more of a piercing point,skewness, pitch, roll, tilt, or source-to-detector distance of themobile C-arm apparatus.
 14. The method of claim 2, further comprisingreceiving, from the detector, the plurality of second images of theanatomic region of the patient, wherein the second images are obtainedduring a second manual rotation of the imaging arm, and wherein movementof the imaging arm relative to the support arm is constrained by thestabilization mechanism during the second manual rotation.
 15. Themethod of claim 14, further comprising receiving, from at least onesensor coupled to the imaging arm, data indicative of a plurality ofposes of the imaging arm during the second manual rotation, wherein the3D reconstruction is generated based on the data indicative of theplurality of poses.
 16. The method of claim 2, wherein the 3Dreconstruction comprises a cone-beam computed tomography reconstruction.17. A system for imaging an anatomic region of a patient, the systemcomprising: one or more processors operably coupled to a mobile C-armapparatus; and a memory operably coupled to the one or more processorsand storing instructions that when executed by the one or moreprocessors, cause the system to perform operations comprising:receiving, from a detector carried by an imaging arm of the mobile C-armapparatus, a plurality of first images of a set of fiducial markers,wherein the first images are obtained during manual rotation of theimaging arm, wherein the mobile C-arm apparatus comprises a support armmovably coupled to the imaging arm, and wherein movement of the imagingarm relative to the support arm is constrained by a stabilizationmechanism during the manual rotation; determining a set of geometriccalibration parameters for the mobile C-arm apparatus based on the firstimages; and generating a 3D reconstruction of the anatomic region of thepatient based on a plurality of second images of the anatomic region andthe geometric calibration parameters.
 18. The system of claim 17,wherein the operations further comprise: before receiving the pluralityof first images, receiving a plurality of third images of a set offiducial markers, wherein the third images are obtained during manualrotation of the imaging arm, and wherein movement of the imaging armrelative to the support arm is constrained by the stabilizationmechanism during the obtaining of the third images; and determining aset of distortion correction parameters for the mobile C-arm apparatusbased on the third images, wherein the 3D reconstruction is generatedbased on the distortion correction parameters.
 19. The system of claim17, further comprising the stabilization mechanism, wherein thestabilization mechanism comprises a shim structure.
 20. The system ofclaim 17, further comprising the stabilization mechanism, wherein thestabilization mechanism comprises: a pair of arm regions; and a bridgeregion connecting the pair of arm regions.
 21. The system of claim 17,further comprising the stabilization mechanism, wherein thestabilization mechanism is configured to fill at least one gap in aninterface between the imaging arm and the support arm.
 22. The system ofclaim 17, wherein the first images are obtained during a propellerrotation of the imaging arm.
 23. The system of claim 17, furthercomprising a phantom comprising the fiducial markers.
 24. The system ofclaim 23, wherein the fiducial markers are arranged in a grid within thephantom.
 25. The system of claim 17, wherein the operations furthercomprise determining, using at least one sensor coupled to the imagingarm, data indicative of a plurality of poses of the imaging arm duringthe manual rotation, wherein the geometric calibration parameters aredetermined based on the data.
 26. The system of claim 25, wherein theoperations further comprise: receiving, from the at least one sensorcoupled to the imaging arm, data indicative of a plurality of secondposes of the imaging arm during a pre-acquisition manual rotation;comparing the data indicative of the plurality of second poses to thedata indicative of the plurality of poses; and outputting feedback to auser based on the comparison.
 27. The system of claim 26, wherein thefeedback comprises feedback regarding one or more of the following:rotation trajectory, rotation speed, orientation of the imaging arm,position of the imaging arm, or stability of the imaging arm.
 28. Thesystem of claim 17, wherein the geometric calibration parameterscomprise one or more of a piercing point, skewness, pitch, roll, tilt,or source-to-detector distance of the mobile C-arm apparatus.
 29. Thesystem of claim 17, wherein the operations further comprise receiving,from the detector, the plurality of second images of the anatomic regionof the patient, wherein the second images are obtained during a secondmanual rotation of the imaging arm, and wherein movement of the imagingarm relative to the support arm is constrained by the stabilizationmechanism during the second manual rotation.
 30. The system of claim 29,wherein the operations further comprise receiving, from at least onesensor coupled to the imaging arm, data indicative of a plurality ofposes of the imaging arm during the second manual rotation, wherein the3D reconstruction is generated based on the data indicative of theplurality of poses.
 31. The system of claim 17, wherein the 3Dreconstruction comprises a cone-beam computed tomography reconstruction.